Modular Synth

Welcome to the documentation for Modular Synth, a node-based modular audio synthesizer built in Rust.

The Modular Synth interface showing a basic patch

What is Modular Synth?

Modular Synth takes a different approach from traditional virtual modular synthesizers. Instead of emulating physical hardware with skeuomorphic interfaces, it uses a clean node-graph approach similar to Blender's node editor or Unreal Engine's Blueprints.

This design philosophy offers several advantages:

• Clarity: Signal flow is immediately visible through color-coded connections
• Flexibility: Modules can be freely arranged without physical constraints
• Efficiency: Clean UI focuses on the essentials without decorative elements
• Learning: The visual representation helps understand synthesis concepts

Design Philosophy

Visual Feedback Over Skeuomorphism

While hardware emulations try to recreate the look of physical synthesizers, Modular Synth prioritizes information density and visual feedback. Every element serves a purpose:

• Color-coded signals tell you instantly what type of data flows through each connection
• Animated knobs show real-time modulation when controlled externally
• Waveform displays provide immediate visual confirmation of signal content

Node Graph Architecture

The node-graph paradigm brings several benefits:

1. Scalable patches: Zoom out to see the big picture, zoom in for details
2. Flexible layout: Arrange modules to match your mental model of the patch
3. Clear connections: Bezier curves with signal-type coloring make routing obvious
4. No cable spaghetti: Connections can cross without confusion thanks to color coding

Signal Types

Modular Synth uses four distinct signal types, each with its own color:

Learn more in Signal Types.

Module Categories

Modules are organized into functional categories, each with a distinctive header color:

• Sources (Blue) - Sound generators like oscillators
• Filters (Green) - Frequency shaping modules
• Modulation (Orange) - Envelopes, LFOs, and clocks
• Utilities (Yellow) - VCAs, mixers, and signal processors
• Effects (Purple) - Delays, reverbs, and other effects
• MIDI (Magenta) - MIDI input and processing
• Output (Red) - Final audio output

Getting Started

Ready to dive in? Here's the recommended path:

1. Installation - Get Modular Synth running on your system
2. Interface Overview - Learn the UI basics
3. Your First Patch - Build a simple synthesizer

Or jump straight to the Module Reference if you're already familiar with modular synthesis.

Technical Foundation

Modular Synth is built with:

• Rust - For performance and safety
• egui - Immediate-mode GUI framework
• cpal - Cross-platform audio I/O
• Lock-free architecture - UI and audio threads communicate without blocking

The audio engine uses pre-allocated buffers and lock-free ring buffers to ensure glitch-free audio processing.

Installation

Modular Synth is built from source using Rust's Cargo build system.

Prerequisites

Rust Toolchain

Install the Rust toolchain via rustup:

# On Windows (PowerShell)
winget install Rustlang.Rustup

# On macOS/Linux
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Verify the installation:

rustc --version
cargo --version

Platform-Specific Dependencies

Windows

No additional dependencies required. The WASAPI audio backend is included with Windows.

macOS

No additional dependencies required. CoreAudio is included with macOS.

Linux

Install the ALSA development libraries:

# Debian/Ubuntu
sudo apt install libasound2-dev

# Fedora
sudo dnf install alsa-lib-devel

# Arch Linux
sudo pacman -S alsa-lib

Building from Source

Clone the Repository

git clone https://github.com/your-repo/modular.git
cd modular

Build and Run

For development (faster compilation, slower runtime):

cargo run

For release (slower compilation, optimized runtime):

cargo run --release

The release build is recommended for actual music-making, as it provides significantly better audio performance with lower CPU usage.

Build Options

Debug Build

cargo build

Creates an unoptimized binary in target/debug/ with debug symbols for development and troubleshooting.

Release Build

cargo build --release

Creates an optimized binary in target/release/ suitable for regular use.

Running Tests

cargo test

Troubleshooting

Audio Device Not Found

If you receive an audio device error:

1. Check that your audio device is connected and working
2. Verify no other application has exclusive access to the audio device
3. Try a different sample rate if available

High CPU Usage

If you experience high CPU usage or audio glitches:

1. Use the release build (cargo run --release)
2. Reduce the number of active modules
3. Check that your audio buffer size is appropriate (larger buffers reduce CPU but increase latency)

Linux: ALSA Underruns

If you experience audio dropouts on Linux:

1. Ensure the ALSA development libraries are installed
2. Try increasing the audio buffer size
3. Consider running with real-time priority (requires appropriate permissions)

Next Steps

Once you have Modular Synth running:

1. Interface Overview - Learn to navigate the UI
2. Your First Patch - Build your first synthesizer

Interface Overview

Modular Synth uses a node-graph interface where modules are represented as nodes that can be connected together to create synthesizer patches.

The main Modular Synth interface

The Canvas

The main area of the interface is the node graph canvas. This is where you create and connect modules.

Navigation

Canvas Tips

• Double-click empty space to quickly add a module
• Use the scroll wheel to zoom in for detailed work or out for an overview
• Modules can be freely positioned anywhere on the canvas

Adding Modules

Context Menu

Right-click on empty canvas space to open the module browser:

The module browser context menu

Modules are organized by category:

• Sources - Oscillators and sound generators
• Filters - Frequency shaping
• Modulation - Envelopes, LFOs, clocks
• Utilities - VCAs, mixers, signal processing
• Effects - Delays, reverbs, distortion
• MIDI - MIDI input and processing
• Visualization - Scopes and meters
• Output - Audio output

Click a module name to add it at the cursor position.

Quick Add

Double-click on empty canvas space to open a quick search box where you can type to filter modules by name.

Module Anatomy

Each module has a consistent structure:

Parts of a module

Header Bar

The colored bar at the top shows:

• Module name - The type of module
• Category color - Indicates the module's function category

Input Ports (Left Side)

Circular connectors on the left side receive signals from other modules:

• Port color indicates the expected signal type
• Port label describes what the input controls
• Hover over a port to see a tooltip with details

Output Ports (Right Side)

Circular connectors on the right side send signals to other modules:

• Port color indicates the signal type produced
• Multiple modules can connect to the same output

Parameter Knobs (Bottom)

Rotary knobs for adjusting module parameters:

• Drag vertically to adjust the value
• Double-click to reset to default
• Ctrl + click for fine adjustment
• Value readout shows the current setting

Exposed Parameters

Some parameters can be controlled both manually and via external signals. When an external signal is connected:

• The knob becomes read-only (dimmed appearance)
• The knob animates to show the incoming signal value
• An orange indicator shows external control is active

When disconnected, the knob returns to manual control.

Making Connections

Creating a Connection

1. Click and hold on an output port (right side of a module)
2. Drag to an input port (left side of another module)
3. Release to complete the connection

Dragging a connection from output to input

Connection Rules

• Outputs connect to inputs (never output-to-output or input-to-input)
• Signal types should match (Audio to Audio, Control to Control, etc.)
• Some inputs accept multiple signal types (automatic conversion)
• Multiple cables can connect to the same output
• Only one cable can connect to each input

Connection Colors

Cables are colored by signal type:

Removing Connections

• Right-click on a connection to delete it
• Click on an input port with an existing connection, then press Escape to disconnect
• Delete a module to remove all its connections

Adjusting Parameters

Knob Interaction

Adjusting a parameter knob

Value Display

Below each knob is a value readout showing:

• The current numeric value
• The unit (Hz, ms, dB, etc.) where applicable

Patch Management

Saving Patches

Patches are saved as .json files containing all module settings and connections.

Loading Patches

Recent Patches

Access recently opened patches from the File menu.

MIDI Setup

Enabling MIDI Input

1. Add a MIDI Note or Keyboard module to your patch
2. The module will automatically receive input from connected MIDI devices

MIDI Learn

To assign a MIDI controller to a knob:

1. Right-click the knob
2. Select MIDI Learn
3. Move the desired MIDI controller
4. The knob is now mapped to that controller

Computer Keyboard

The Keyboard module allows playing notes using your computer keyboard:

• Z-M row: Lower octave (C3-B3)
• Q-P row: Upper octave (C4-B4)
• Number keys: Octave selection

Keyboard Shortcuts

General

Navigation

Modules

Next Steps

Now that you understand the interface:

• Your First Patch - Build a simple synthesizer step by step
• Signal Types - Understand the different signal types
• Module Reference - Explore all available modules

Your First Patch

Let's build a simple synthesizer patch from scratch. By the end of this tutorial, you'll have a playable synthesizer with an oscillator, filter, envelope, and output.

The completed first patch

Step 1: Add an Oscillator

Every synthesizer needs a sound source. Let's start with an oscillator.

1. Right-click on the canvas to open the module browser
2. Navigate to Sources > Oscillator
3. Click to add the oscillator

Adding an oscillator from the context menu

The oscillator generates a continuous tone. By default, it produces a sine wave at 440 Hz (the note A4).

Oscillator Settings

• Waveform: Select between Sine, Saw, Square, or Triangle
• Frequency: The pitch in Hz (or controlled by V/Oct input)
• Detune: Fine-tune adjustment in cents

Try changing the waveform to Saw for a brighter, more harmonically rich sound.

Step 2: Add Audio Output

To hear the oscillator, we need to connect it to the audio output.

1. Right-click on the canvas
2. Navigate to Output > Audio Output
3. Click to add the output module

Position it to the right of the oscillator.

Connect the Oscillator to Output

1. Click on the oscillator's Audio Out port (right side, blue)
2. Drag to the output's Left input port
3. Release to create the connection

Connecting the oscillator to the output

You should now hear a continuous tone! If not, check that:

• Your audio device is working
• The output module's Level knob is turned up
• Your system volume is audible

Stereo Output

For stereo sound, also connect the oscillator to the Right input, or use the Mono input which sends to both channels.

Step 3: Control the Pitch

A synthesizer that plays only one note isn't very useful. Let's add keyboard control.

1. Right-click > MIDI > Keyboard Input
2. Position it to the left of the oscillator

Connect Keyboard to Oscillator

1. Connect the keyboard's V/Oct output to the oscillator's V/Oct input
2. Connect the keyboard's Gate output (we'll use this later)

Keyboard controlling the oscillator pitch

Now press keys on your computer keyboard:

• Z, X, C, V, B, N, M play notes C through B
• A, S, D, F, G, H, J play sharps/flats
• Q-P row plays an octave higher

The oscillator pitch follows your keyboard input!

Step 4: Add an Envelope

Right now, the sound plays continuously. An envelope shapes the sound over time, giving it a beginning and end.

1. Right-click > Modulation > ADSR Envelope
2. Position it between the keyboard and output

Envelope Parameters

The ADSR envelope has four stages:

• Attack: How quickly the sound rises (0 = instant, higher = gradual fade in)
• Decay: How quickly it falls to the sustain level
• Sustain: The level held while the key is pressed
• Release: How quickly the sound fades after key release

Set these initial values:

• Attack: 10ms (quick start)
• Decay: 200ms (moderate decay)
• Sustain: 0.5 (half volume while held)
• Release: 300ms (gentle fade out)

Connect the Envelope

1. Connect the keyboard's Gate output to the envelope's Gate input
2. Connect the envelope's Env output to... we need a VCA!

Step 5: Add a VCA

A VCA (Voltage Controlled Amplifier) controls the volume of a signal. We'll use it to apply the envelope to our oscillator.

1. Right-click > Utilities > VCA
2. Position it between the oscillator and output

Connect Everything

1. Disconnect the oscillator from the output (right-click the cable)
2. Connect the oscillator's Audio Out to the VCA's Input
3. Connect the envelope's Env output to the VCA's CV input
4. Connect the VCA's Output to the audio output's Mono input

The patch with VCA and envelope

Now when you press a key:

• The keyboard sends Gate and V/Oct
• The envelope responds to the Gate
• The VCA shapes the oscillator volume based on the envelope

Try adjusting the envelope parameters to change the character of the sound!

Step 6: Add a Filter

Filters shape the harmonic content of a sound by removing frequencies. Let's add a low-pass filter to warm up our tone.

1. Right-click > Filters > SVF Filter
2. Position it between the oscillator and VCA

Connect the Filter

1. Disconnect the oscillator from the VCA
2. Connect oscillator Audio Out to filter Input
3. Connect filter Lowpass output to VCA Input

Filter Settings

• Cutoff: The frequency where filtering begins (lower = darker sound)
• Resonance: Emphasizes frequencies at the cutoff (creates a peak)

Set cutoff to around 1000 Hz and resonance to 0.3 for a warm, slightly vocal quality.

Adding the SVF filter to the signal chain

Step 7: Modulate the Filter (Optional)

For a more dynamic sound, let's make the filter open and close with each note using the envelope.

Add Filter Envelope Control

You can use the same envelope or add a second one:

1. Connect the envelope's Env output to the filter's Cutoff input

Now the filter cutoff follows the envelope shape:

• Filter opens during attack
• Closes during decay
• Stays partially open during sustain
• Closes during release

Adjust the Cutoff knob to set the baseline, and the envelope adds movement on top.

Complete Patch Overview

Here's the final signal flow:

[Keyboard] ──V/Oct──> [Oscillator] ──Audio──> [Filter] ──Audio──> [VCA] ──Audio──> [Output]
    │                                            ↑                   ↑
    └───────Gate────> [ADSR Envelope] ───────────┴───────────────────┘

The complete first patch

What You've Learned

• Adding modules from the context menu
• Connecting modules by dragging between ports
• Signal flow: Oscillator → Filter → VCA → Output
• Control signals: Gate triggers the envelope, V/Oct controls pitch
• Modulation: Using the envelope to control both VCA and filter

Experimentation Ideas

Try these modifications:

1. Change the waveform - Saw and Square have more harmonics for the filter to work with
2. Add an LFO - Connect it to the filter cutoff for a wobbling effect
3. Increase resonance - Higher resonance creates a more dramatic filter sweep
4. Adjust envelope - Long attack creates pad sounds, short attack creates plucks
5. Add reverb - Insert a reverb effect between VCA and output

Next Steps

Now that you've built your first patch:

• Signal Types - Understand the different signal types in depth
• Module Reference - Explore all available modules
• Basic Subtractive Synth - A more complete subtractive synthesizer recipe
• FM Synthesis - Try a different synthesis technique

Signal Types

Modular Synth uses a type system for signals that helps you understand what kind of data flows through each connection. Each signal type has a distinctive color, making it easy to trace the flow of audio, control, gate, and MIDI signals through your patch.

Overview

The four signal types with their colors

Audio Signals

Color: Blue

Audio signals carry the actual sound you hear. They oscillate rapidly (typically 20 Hz to 20 kHz) and represent the waveform that will be sent to your speakers.

Characteristics

• Range: -1.0 to 1.0 (bipolar)
• Sample Rate: Matches your audio interface (typically 44.1 kHz or 48 kHz)
• Bandwidth: Full audio spectrum

Common Sources

• Oscillators (all waveforms)
• Filter outputs
• Effect outputs
• Sample playback

Common Destinations

• Filter inputs
• Effect inputs
• VCA inputs
• Audio Output module

Signal Level

Audio signals should stay within the -1.0 to 1.0 range to avoid clipping (distortion). The Audio Output module includes a limiter to prevent harsh digital clipping, but it's best to manage levels throughout your patch.

Control Signals

Color: Orange

Control signals (also called CV or Control Voltage) carry slower-moving data used to modulate parameters. They don't produce sound directly but shape and control other modules.

Characteristics

• Unipolar Range: 0.0 to 1.0 (e.g., envelope output, LFO with offset)
• Bipolar Range: -1.0 to 1.0 (e.g., bipolar LFO)
• Bandwidth: Typically low frequency (< 100 Hz), but can be audio rate

Common Sources

• Envelopes (ADSR)
• LFOs
• Sequencers
• MIDI CC (converted to CV)
• Attenuverters

Common Destinations

• Filter cutoff
• Oscillator frequency (FM)
• VCA CV input
• Effect parameters
• Any "modulatable" parameter

Unipolar vs. Bipolar

Unipolar (0.0 to 1.0):

• Always positive
• Good for controlling parameters that shouldn't go negative
• Examples: envelope output, volume control

Bipolar (-1.0 to 1.0):

• Swings positive and negative
• Good for vibrato, filter sweeps that go both ways
• Examples: LFO output, pitch modulation

V/Oct (Volts per Octave)

A special control signal convention where each 1.0 increase represents one octave up in pitch. This allows precise musical pitch control:

• 0.0 = Base frequency (e.g., C0)
• 1.0 = One octave up (C1)
• 2.0 = Two octaves up (C2)
• 0.5 = Half octave up (F#0)
• -1.0 = One octave down (C-1)

The Keyboard and MIDI Note modules output V/Oct signals for controlling oscillator pitch.

Gate Signals

Color: Green

Gate signals are binary on/off signals used for triggering events. Unlike audio or control signals that vary continuously, gates are either fully on (1.0) or fully off (0.0).

Characteristics

• Range: 0.0 (off) or 1.0 (on)
• Transitions: Rising edge (0→1) and falling edge (1→0)
• Duration: The time the gate stays high

Gate vs. Trigger

While both use the green color, there's a conceptual difference:

Gate: Stays high for a duration (like holding a key)

• Used for: Envelope gate input, held notes

Trigger: Brief pulse (like a drum hit)

• Used for: Clock pulses, one-shot events

Most modules respond appropriately to both.

Common Sources

• Keyboard/MIDI Note (key pressed/released)
• Clock modules (rhythmic pulses)
• Sequencers (step triggers)
• LFOs in square wave mode

Common Destinations

• Envelope gate input
• Sample & Hold trigger
• Sequencer clock input
• Any module that responds to triggers

Edge Detection

Some modules respond to:

• Rising edge: The moment gate goes from 0 to 1
• Falling edge: The moment gate goes from 1 to 0
• Gate high: While the gate is 1
• Gate low: While the gate is 0

For example, an ADSR envelope:

• Begins Attack on rising edge
• Enters Release on falling edge

MIDI Signals

Color: Purple

MIDI signals carry structured musical data including note events, control changes, and other MIDI messages. Unlike the other signal types which are continuous values, MIDI signals contain discrete events.

Characteristics

• Format: Structured messages (Note On/Off, CC, etc.)
• Data: Note number, velocity, channel, CC values
• Timing: Event-based rather than continuous

Common Sources

• MIDI Note module (from external MIDI devices)
• Keyboard module (from computer keyboard)

Common Destinations

• MIDI Monitor (for debugging)
• Modules that accept MIDI input directly

MIDI to CV Conversion

Most modules don't work with MIDI directly. The MIDI Note module converts MIDI to:

• V/Oct: Note number → pitch CV
• Gate: Note On/Off → gate signal
• Velocity: Note velocity → control signal

This conversion allows standard synthesis modules to respond to MIDI input.

Signal Type Compatibility

Automatic Conversion

Some connections perform automatic conversion:

Best Practices

While some conversions work, it's best to match signal types:

1. Audio to audio: Full bandwidth sound processing
2. Control to control: Modulation and CV routing
3. Gate to gate: Trigger and timing signals
4. MIDI to MIDI modules: Then convert to CV

Audio-Rate Modulation

Control signals can run at audio rate for special effects:

• FM Synthesis: Audio-rate modulation of oscillator frequency
• Ring Modulation: Audio-rate amplitude modulation
• Filter FM: Audio-rate cutoff modulation for unusual timbres

Visual Identification

Port Colors

Input and output ports are colored to indicate the expected signal type:

Ports showing their signal type colors

Cable Colors

Cables inherit the color of the signal they carry, making it easy to trace signal flow:

Cables colored by signal type

Module Headers

Module header colors indicate the category, not signal type:

• Blue header = Source (produces audio signals)
• Green header = Filter (processes audio signals)
• Orange header = Modulation (produces control signals)
• etc.

Next Steps

• Connections - Learn the rules for connecting modules
• Module Reference - See signal types for each module

Connections

Connections are the cables that link modules together, allowing signals to flow through your patch. Understanding connection rules helps you build effective synthesizer patches.

Basic Rules

Outputs to Inputs

Connections always flow from output ports (right side of modules) to input ports (left side of modules).

Signals flow from outputs (right) to inputs (left)

You cannot:

• Connect output to output
• Connect input to input
• Create circular connections that would cause feedback loops (the system prevents this)

One Input, Many Outputs

Inputs accept only one connection at a time. Connecting a new cable to an already-connected input will replace the existing connection.

Outputs can feed multiple inputs. The signal is copied to each destination without reduction in level.

One output feeding multiple inputs

Making Connections

Creating a Connection

1. Click and hold on an output port
2. Drag toward the destination input
3. The cursor will show valid connection points
4. Release over an input port to complete

Dragging to create a connection

Visual Feedback

While dragging:

• Valid inputs highlight to show they can accept the connection
• Invalid inputs (wrong signal type or already connected) may dim
• The cable preview shows the signal type color

Quick Connect

Double-click an output port to start a connection, then single-click an input to complete it. This is useful for long-distance connections.

Removing Connections

Right-Click Method

Right-click on a cable to delete it immediately.

Disconnect from Port

Click on a connected input port, then press Escape to disconnect.

Delete Module

Deleting a module automatically removes all its connections.

Signal Type Matching

Preferred Connections

For best results, match signal types:

Cross-Type Connections

Some cross-type connections are useful:

The system allows most cross-type connections, treating the signal according to the destination's expectations.

MIDI Special Case

MIDI signals are structured differently and generally only connect to MIDI-specific inputs. Use the MIDI Note module to convert MIDI to CV signals (V/Oct, Gate, Velocity) for standard modules.

Cable Colors

Cables are colored by signal type for easy visual identification:

Cables colored by signal type

This coloring helps you:

• Trace signal flow through complex patches
• Identify signal types at a glance
• Debug routing issues

Connection Tips

Keep It Organized

• Position modules so signal flows left-to-right
• Group related modules together
• Use the canvas space to prevent cable crossings

A well-organized patch with clear signal flow

Modulation Routing

Control signals often "reach across" the main signal flow:

[LFO] ────────────────────────┐
                              ↓ (CV)
[Osc] ──> [Filter] ──> [VCA] ──> [Out]
            ↑
[Envelope] ─┘

Position modulation sources (LFOs, envelopes) above or below the main signal path.

Check Signal Flow

If you're not getting sound:

1. Trace from output backward - Is the Audio Output connected?
2. Check control signals - Is the VCA getting a CV signal?
3. Verify gates - Is the envelope receiving a gate?
4. Look at signal types - Are the right types connected?

Exposed Parameters

Some module parameters can be controlled via connections. These are called "exposed" parameters.

How It Works

When a parameter is exposed:

• It has both a knob for manual control AND an input port for external control
• When disconnected: The knob controls the parameter normally
• When connected: The external signal takes over

Visual Indicators

An exposed parameter showing external control

When externally controlled:

• The knob becomes read-only (dimmed)
• The knob animates to show the incoming signal value
• An orange indicator dot shows external control is active

Combining Manual and Modulation

The external signal often adds to the knob's base value:

• Knob sets the center/base value
• Input adds modulation on top

For example, a filter cutoff:

• Knob at 1000 Hz
• LFO input swinging ±500 Hz
• Result: Cutoff sweeps between 500-1500 Hz

Advanced Topics

Audio-Rate Modulation

Control inputs can accept audio-rate signals for special effects:

• FM Synthesis: Oscillator frequency modulated at audio rate
• AM/Ring Mod: Amplitude modulated at audio rate
• Filter FM: Cutoff modulated at audio rate

Feedback Loops

The system prevents direct feedback loops (output connecting back to earlier input in the same signal path). This is necessary to maintain stable, real-time audio processing.

For delay-based feedback effects, use the Delay module's built-in feedback control.

DC Offset

Control signals may have DC offset (a constant value added to the signal). Some modules include DC blocking or offset controls to manage this.

Troubleshooting

No Sound

1. Check that Audio Output is connected
2. Verify VCA is receiving CV or is set to pass audio
3. Ensure oscillator is running (not waiting for trigger)
4. Check system audio settings

Unexpected Sound

1. Look for unintended connections
2. Check signal levels (may need attenuation)
3. Verify signal types match expectations

Clicking or Popping

1. Ensure control signals are smoothed
2. Check for abrupt gate transitions
3. Add slight attack/release to envelopes

Next Steps

• Module Reference - See connection details for each module
• Your First Patch - Practice making connections

Module Overview

Modular Synth includes 22 modules organized into functional categories. Each category has a distinctive header color for quick identification.

Categories

Sources (Blue Header)

Sound generators that create audio signals from scratch.

Filters (Green Header)

Frequency-shaping modules that remove or emphasize parts of the spectrum.

Modulation (Orange Header)

Modules that generate control signals for modulating other parameters.

Utilities (Yellow Header)

Signal processing and routing modules.

Effects (Purple Header)

Audio processing effects.

MIDI (Magenta Header)

MIDI input and processing modules.

Visualization (Cyan Header)

Visual feedback modules.

Output (Red Header)

Final audio output.

Signal Type Quick Reference

When connecting modules, match these signal types:

Common Signal Chains

Basic Synthesis Path

[Oscillator] → [Filter] → [VCA] → [Output]

With Modulation

[Keyboard] ──V/Oct──→ [Oscillator] → [Filter] → [VCA] → [Output]
    │                                    ↑         ↑
    └──Gate──→ [Envelope] ──────────────┴─────────┘

With Effects

[Oscillator] → [Filter] → [VCA] → [Delay] → [Reverb] → [Output]

Sequenced Pattern

[Clock] → [Sequencer] ──CV──→ [Oscillator] → [Filter] → [Output]
              │                                  ↑
              └──Gate──→ [Envelope] ────────────┘

Choosing Modules

I want to...

Generate a sound: Start with Oscillator

Shape the tone: Use SVF Filter

Control volume: Use VCA with an Envelope

Add movement: Connect an LFO to a parameter

Play from keyboard: Add Keyboard Input or MIDI Note

Create rhythmic patterns: Use Clock and Sequencer

Add space/depth: Use Delay or Reverb

Mix multiple signals: Use Mixer

See what's happening: Add Oscilloscope

Hear the result: Connect to Audio Output

Oscillator

Module ID: osc.sine Category: Sources Header Color: Blue

The Oscillator module

Description

The Oscillator is the primary sound source in Modular Synth. It generates periodic waveforms at audio frequencies, producing the raw tones that can be shaped by filters, envelopes, and effects.

This is a VCO (Voltage Controlled Oscillator), meaning its frequency can be controlled by external signals, enabling keyboard tracking and vibrato effects.

Inputs

Outputs

Parameters

Waveforms

Sine

Pure tone with no harmonics. Useful for:

• Sub-bass
• FM synthesis carriers
• Pure, flute-like tones
• Smooth modulation sources

Sawtooth (Saw)

Contains all harmonics with decreasing amplitude. Useful for:

• Classic synth leads and basses
• Strings and brass sounds
• Rich source material for filtering

Square

Contains odd harmonics only. Useful for:

• Hollow, woody tones
• Clarinet-like sounds
• PWM for chorus-like effects

Triangle

Contains odd harmonics with rapid rolloff. Useful for:

• Softer than square, brighter than sine
• Flute and soft lead sounds
• Smooth modulation

Usage Tips

Basic Pitch Control

Connect a keyboard or MIDI module's V/Oct output to control pitch:

[Keyboard] ──V/Oct──> [Oscillator]

The V/Oct standard means:

• 0.0 = Base frequency (set by Frequency knob)
• 1.0 = One octave up
• -1.0 = One octave down
• 0.083 = One semitone up (1/12 of an octave)

Vibrato with LFO

Connect an LFO to the FM input for vibrato:

[LFO] ──> [Oscillator FM]

• Use low FM Amount (0.1-0.2) for subtle vibrato
• Higher amounts create more dramatic pitch wobble
• LFO rate of 5-7 Hz is typical for vibrato

FM Synthesis

Connect another oscillator to FM input for FM synthesis:

[Oscillator 2] ──> [Oscillator 1 FM]

• Sine waves work best for clean FM tones
• Integer frequency ratios (2:1, 3:1) create harmonic sounds
• Non-integer ratios create inharmonic, bell-like tones
• FM Amount controls brightness/complexity

Pulse Width Modulation

For square wave, modulate pulse width with an LFO:

[LFO] ──> [Oscillator PWM]

• Creates a chorus-like, animated effect
• Extreme PW values (near 0.1 or 0.9) create thin, nasal tones
• Slow LFO rates create subtle movement
• Fast rates create more dramatic timbral changes

Hard Sync

Connect a sync signal to reset the waveform cycle:

[Oscillator 2 Out] ──> [Oscillator 1 Sync]

Hard sync creates complex, aggressive tones:

• Oscillator 1 (synced) resets when Oscillator 2 completes a cycle
• Sweep Oscillator 1's frequency for the classic sync sweep sound
• Works best when synced osc is higher frequency than master

Detuning for Thickness

Use two oscillators slightly detuned for a thicker sound:

[Osc 1 (Detune: 0)] ──┐
                      ├──> [Mixer] ──> [Filter]
[Osc 2 (Detune: +7)] ─┘

• Small detune values (5-15 cents) create subtle chorusing
• Larger values (20-50 cents) create a "supersaw" effect

Connection Examples

Typical Synthesis Chain

[Keyboard] ──V/Oct──> [Oscillator] ──> [Filter] ──> [VCA] ──> [Output]

FM Bell Patch

[Oscillator 1] ──FM──> [Oscillator 2] ──> [VCA] ──> [Output]
     (Modulator)           (Carrier)

Dual Oscillator with PWM

[LFO] ──> [Osc 1 PWM]
          [Osc 1] ──┐
                    ├──> [Mixer] ──> [Filter]
          [Osc 2] ──┘

Related Modules

• LFO - For vibrato and PWM modulation
• SVF Filter - Shape the oscillator's harmonics
• VCA - Control oscillator volume
• ADSR Envelope - Shape the sound over time

SVF Filter

Module ID: filter.svf Category: Filters Header Color: Green

The SVF Filter module

Description

The State Variable Filter (SVF) is a versatile multi-mode filter that provides simultaneous lowpass, highpass, and bandpass outputs from a single input signal. This architecture allows you to blend different filter responses or switch between them without repatching.

The SVF design offers:

• Self-oscillation at high resonance (can be used as a sine oscillator)
• Smooth cutoff sweeps without artifacts
• Stable operation across all settings
• Simultaneous multi-mode outputs

Inputs

Outputs

Parameters

Filter Modes

Lowpass (LP)

Lowpass frequency response

• Passes frequencies below the cutoff
• Removes high frequencies, creating a "darker" or "warmer" sound
• Most common filter type for synthesis
• At 12dB/octave slope (2-pole)

Use cases:

• Warming up bright oscillators
• Classic subtractive synthesis
• Bass sounds
• Removing harshness

Highpass (HP)

Highpass frequency response

• Passes frequencies above the cutoff
• Removes low frequencies, creating a "thinner" or "brighter" sound
• At 12dB/octave slope (2-pole)

Use cases:

• Removing mud/rumble
• Creating thin, airy sounds
• Hi-hat and cymbal synthesis
• Clearing space in a mix

Bandpass (BP)

Bandpass frequency response

• Passes frequencies around the cutoff
• Removes both low and high frequencies
• Width controlled by resonance

Use cases:

• Vocal/formant-like sounds
• Telephone/radio effect
• Isolating specific frequency ranges
• Wah-wah effects

Usage Tips

Basic Filtering

Connect an oscillator to soften its harmonics:

[Oscillator] ──> [Filter Input]
                 [Filter LP] ──> [VCA] ──> [Output]

• Start with cutoff around 1000 Hz
• Adjust cutoff to taste - lower = darker, higher = brighter
• Add slight resonance (0.2-0.4) for character

Filter Envelope

Create dynamic filter sweeps with an envelope:

[Keyboard] ──Gate──> [Envelope] ──> [Filter Cutoff CV]

• Set base cutoff low (200-500 Hz)
• Use positive CV Amount
• Short attack/decay creates "plucky" sounds
• Long attack creates "swelling" sounds

Filter + LFO (Wobble)

Create rhythmic filter movement:

[LFO] ──> [Filter Cutoff CV]

• Square LFO creates choppy, rhythmic effect
• Triangle/Sine LFO creates smooth wobble
• Adjust LFO rate and CV Amount for intensity

Self-Oscillation

At high resonance (near 1.0), the filter will self-oscillate, producing a sine wave at the cutoff frequency:

• Set resonance to ~0.95 or higher
• No input signal needed
• Control pitch via Cutoff CV
• Useful for pure sine tones and sound effects

Note: Self-oscillation can be loud - reduce output level first.

Tracking Keyboard

Make filter cutoff follow the keyboard:

[Keyboard] ──V/Oct──> [Oscillator V/Oct]
           ──V/Oct──> [Filter Cutoff CV]

This keeps the filter's relative brightness consistent across different pitches. Set CV Amount to achieve 1:1 tracking.

Parallel Filter Modes

Use multiple outputs simultaneously for complex sounds:

[Oscillator] ──> [Filter Input]
                 [Filter LP] ──> [Mixer Ch1]
                 [Filter BP] ──> [Mixer Ch2] ──> [Output]

Blend lowpass and bandpass for unique timbres.

Resonant Accents

High resonance emphasizes the cutoff frequency:

• Creates a "peak" or "ping" at the cutoff
• Useful for acid bass lines (TB-303 style)
• Combine with filter envelope for accent effects

Notch Filter (Advanced)

Combine highpass and lowpass outputs to create a notch:

[Filter LP] ──> [Mixer] (inverted) ──┐
[Filter HP] ──> [Mixer] ─────────────┴──> [Output]

The phase relationship creates a notch at the cutoff frequency.

Connection Examples

Classic Subtractive Synth

[Keyboard] ──V/Oct──> [Oscillator] ──> [Filter] ──> [VCA] ──> [Output]
           ──Gate───> [Envelope] ──────────┬─────────────┘
                                           └──> [Filter Cutoff CV]

Acid Bass

[Sequencer] ──CV──> [Oscillator (Saw)] ──> [Filter LP] ──> [Output]
            ──Gate──> [Envelope] ──> [Filter Cutoff CV]
                                     (Resonance: 0.7-0.9)

Wah Effect

[Guitar/Audio In] ──> [Filter BP] ──> [Output]
                      [Expression Pedal] ──> [Filter Cutoff CV]

Sound Design Tips

Related Modules

• Oscillator - Primary input source
• ADSR Envelope - Modulate cutoff over time
• LFO - Create filter wobble effects
• VCA - Control filtered output level

ADSR Envelope

Module ID: mod.adsr Category: Modulation Header Color: Orange

The ADSR Envelope module

Description

The ADSR Envelope generates a control signal that shapes how a sound evolves over time. When triggered by a gate signal (like pressing a key), it produces a predictable voltage curve through four stages: Attack, Decay, Sustain, and Release.

Envelopes are essential for:

• Controlling amplitude (volume shape) via VCA
• Modulating filter cutoff for timbral changes
• Adding dynamic movement to any parameter

Inputs

Outputs

Parameters

Envelope Stages

The four stages of an ADSR envelope

Attack

The Attack phase begins when the gate goes high (key pressed). The envelope rises from 0 to its peak value (1.0).

• Short attack (0.1-10 ms): Instant, percussive start (drums, plucks)
• Medium attack (10-100 ms): Soft start (strings, pads)
• Long attack (100 ms+): Gradual swell (ambient, swells)

Decay

The Decay phase begins immediately after Attack reaches peak. The envelope falls from peak (1.0) to the Sustain level.

• Short decay (10-50 ms): Percussive, plucky sounds
• Medium decay (50-200 ms): Piano-like sounds
• Long decay (200 ms+): Smooth, gradual transition

Sustain

The Sustain phase holds at a fixed level while the gate remains high (key held). Unlike the other parameters (which are times), Sustain is a level from 0.0 to 1.0.

• Low sustain (0.0-0.3): Percussive, the sound dies away while key is held
• Medium sustain (0.3-0.7): Balanced, natural decay to held level
• High sustain (0.7-1.0): Full, organ-like sustained sound

Release

The Release phase begins when the gate goes low (key released). The envelope falls from the current level to 0.

• Short release (10-50 ms): Abrupt stop, staccato
• Medium release (50-300 ms): Natural fade
• Long release (300 ms+): Lingering, ambient tails

Usage Tips

Basic Volume Envelope

Connect envelope to VCA for note-shaped volume:

[Keyboard] ──Gate──> [ADSR] ──> [VCA CV]
[Oscillator] ──> [VCA In] ──> [Output]

Filter Envelope

Create dynamic timbral changes:

[Keyboard] ──Gate──> [ADSR] ──> [Filter Cutoff CV]

• Fast attack + fast decay = "plucky" brightness
• Slow attack = gradual brightening
• Combine with VCA envelope for complex shapes

Dual Envelopes

Use separate envelopes for amplitude and filter:

[Keyboard Gate] ──> [ADSR 1] ──> [VCA CV] (volume shape)
                ──> [ADSR 2] ──> [Filter CV] (timbre shape)

This allows independent control:

• VCA envelope: Long release for sustained notes
• Filter envelope: Short decay for initial brightness

Inverted Envelope

Use the Inv output for "reversed" modulation:

[ADSR Inv] ──> [Filter Cutoff CV]

• Filter opens as note releases
• Creates unusual, "backwards" effects

End of Cycle Triggering

Use EOC output to trigger other events:

[ADSR EOC] ──> [Another ADSR Gate]

• Chain envelopes for complex shapes
• Trigger samples when envelope completes
• Create automatic sequences

Retrigger Behavior

The Retrig input restarts the envelope from Attack:

[LFO Square] ──> [ADSR Retrig]

• Creates rhythmic retriggering
• Useful for tremolo-like effects
• Each trigger restarts the Attack phase

Looping Envelope

Create a looping envelope by connecting EOC to Gate:

[ADSR EOC] ──> [ADSR Gate]

This creates a repeating cycle (like a complex LFO). Adjust A, D, S, R to shape the loop.

Common Envelope Shapes

Pluck (Piano, Guitar)

Fast attack, immediate decay to silence, short release.

Pad (Strings, Ambient)

Slow attack, gradual decay, sustained level, long release.

Organ (Sustained)

Instant attack, no decay, full sustain, quick release.

Brass (Soft Attack)

Moderate attack (breath), slight decay, high sustain.

Percussion (Drum, Pluck)

Instant attack, quick decay, no sustain.

Connection Examples

Standard Synth Voice

[Keyboard] ──V/Oct──> [Oscillator] ──> [Filter] ──> [VCA] ──> [Output]
           ──Gate───> [ADSR 1] ─────────────────────┘
                      [ADSR 2] ──> [Filter Cutoff CV]

Triggered Drone

[Clock] ──> [ADSR Gate]
            [ADSR] ──> [VCA CV]
[Oscillator] ──> [VCA] ──> [Output]

Envelope Following

[ADSR] ──> [Attenuverter] ──> [Multiple Destinations]

Related Modules

• VCA - Control amplitude with envelope
• SVF Filter - Modulate filter with envelope
• Keyboard Input - Gate source for envelope
• LFO - Alternative modulation source

LFO

Module ID: mod.lfo Category: Modulation Header Color: Orange

The LFO module

Description

The Low Frequency Oscillator (LFO) generates slow, cyclic waveforms used for modulation rather than audio. LFOs add movement and animation to your patches by continuously varying parameters like filter cutoff, oscillator pitch, or amplitude.

While structurally similar to audio oscillators, LFOs typically operate at sub-audio frequencies (0.01 Hz to ~20 Hz), creating effects like vibrato, tremolo, and filter sweeps.

Inputs

Outputs

Parameters

Waveforms

Sine

Smooth, continuous modulation with no sharp edges.

Best for:

• Vibrato (pitch modulation)
• Gentle filter sweeps
• Smooth tremolo
• Natural-sounding movement

Triangle

Linear up/down movement with turnaround points.

Best for:

• Similar to sine but with more "edge"
• Classic synthesizer modulation
• Steady back-and-forth motion

Square

Instant switching between minimum and maximum.

Best for:

• Rhythmic on/off effects
• Hard tremolo/chopping
• Sample & Hold-like stepping
• Gate-like modulation

Sawtooth

Gradual rise followed by instant reset.

Best for:

• Rising filter sweeps
• Rhythmic builds
• Asymmetric modulation

Usage Tips

Vibrato

Classic pitch wobble effect:

[LFO] ──> [Oscillator FM]

• Rate: 5-7 Hz for natural vibrato
• Waveform: Sine or Triangle
• Depth: Low FM Amount on oscillator
• Bipolar: On (pitch goes up AND down)

Tremolo

Volume modulation effect:

[LFO] ──> [VCA CV]

• Rate: 4-8 Hz for classic tremolo
• Waveform: Sine (smooth) or Triangle
• Bipolar: Off (volume only goes down from max)

Filter Sweep (Wobble)

Rhythmic filter movement:

[LFO] ──> [Filter Cutoff CV]

• Rate: Sync to tempo for rhythmic effect
• Waveform:
  • Sine/Triangle = smooth wobble
  • Square = choppy rhythm
  • Saw = rising sweeps
• Bipolar: Usually Off

PWM (Pulse Width Modulation)

Animate square wave timbre:

[LFO] ──> [Oscillator PWM]

• Rate: 0.5-3 Hz for subtle animation
• Waveform: Triangle or Sine
• Creates chorus-like thickening

Tempo Sync

Lock LFO to musical time by triggering sync from a clock:

[Clock] ──> [LFO Sync]

The LFO resets its phase on each clock pulse, synchronizing to the tempo.

Phase Offset

Use the Phase parameter when running multiple LFOs:

[LFO 1 (Phase: 0°)] ──> [Osc 1 FM]
[LFO 2 (Phase: 180°)] ──> [Osc 2 FM]

This creates movement that's related but not identical.

Using the Square Output

The dedicated Square output is useful for:

• Triggering envelopes rhythmically
• Creating rhythmic gates
• Sample & Hold clock

[LFO Square] ──> [ADSR Gate]

Unipolar vs Bipolar

Unipolar (0 to 1):

• Filter cutoff (always positive)
• Volume (can't go negative)
• Most parameters

Bipolar (-1 to +1):

• Pitch modulation (up AND down)
• Pan modulation (left AND right)
• Any parameter where negative makes sense

Modulating the Rate

Create evolving modulation by controlling LFO speed:

[LFO 2 (slow)] ──> [LFO 1 Rate CV]

The modulation speed itself varies over time.

Common Settings

Subtle Vibrato

Dramatic Wobble

Rhythmic Chop

Slow Evolution

PWM Animation

Connection Examples

Multi-Destination Modulation

[LFO] ──> [Filter Cutoff CV]
      ──> [Oscillator PWM]
      ──> [VCA CV] (via Attenuverter)

Stereo Movement

[LFO (Phase: 0°)] ──> [Left Channel Parameter]
[LFO (Phase: 90°)] ──> [Right Channel Parameter]

Stepped Random (with S&H)

[LFO] ──> [Sample & Hold Input]
[LFO Square] ──> [Sample & Hold Trigger]
[S&H Output] ──> [Modulation Destination]

LFO vs Envelope

Use LFO for ongoing animation, envelopes for note-shaped modulation.

Related Modules

• ADSR Envelope - Event-triggered modulation
• Clock - For LFO sync
• VCA - Tremolo destination
• SVF Filter - Filter modulation destination
• Oscillator - Vibrato/FM destination

Clock

Module ID: mod.clock Category: Modulation Header Color: Orange

The Clock module

Description

The Clock module generates rhythmic pulse signals at a specified tempo. It's the heartbeat of sequenced and rhythmic patches, providing timing signals to sequencers, envelopes, sample & hold circuits, and any module that needs regular triggers.

The clock outputs multiple synchronized divisions of the main tempo, allowing complex polyrhythmic patterns from a single clock source.

Inputs

Outputs

Parameters

Understanding Divisions

Clock divisions relate to musical note values:

At 120 BPM:

• 1/4 note = 2 pulses per second (500ms apart)
• 1/8 note = 4 pulses per second (250ms apart)
• 1/16 note = 8 pulses per second (125ms apart)

Usage Tips

Basic Sequencer Clocking

Drive a sequencer at eighth-note speed:

[Clock 1/8] ──> [Sequencer Clock In]

Multiple Rhythmic Elements

Use different divisions for different parts:

[Clock 1/4] ──> [Kick Envelope Gate]
[Clock 1/8] ──> [Hi-Hat Envelope Gate]
[Clock 1/16] ──> [Sequencer Clock]

Adding Swing

Swing shifts every other pulse slightly late, creating a "groove" feel:

• 0%: Straight, mechanical timing
• 25%: Light swing, subtle groove
• 50%: Medium swing, jazzy feel
• 67%: Heavy swing, triplet-like
• 75%: Maximum swing, very loose

Swing is applied to the even-numbered pulses of each division.

Syncing LFOs

Reset LFO phase on each beat:

[Clock 1/4] ──> [LFO Sync]

This ensures the LFO always starts at the same point on each beat.

Reset for Song Start

Use reset to synchronize everything:

[Start Button] ──> [Clock Reset]
                   [Clock Run]

Reset brings all divisions back to beat 1, ensuring everything starts together.

External Clock Sync

Sync to external gear or DAW:

[MIDI Clock In] ──> [Clock Ext Clock]

When Ext Clock is connected, the internal BPM is ignored and the clock follows the external tempo.

Creating Polyrhythms

Combine divisions for polyrhythmic patterns:

[Clock 1/4] ──> [Sequencer A Clock] (4 steps)
[Clock 1/8] ──> [Sequencer B Clock] (6 steps)

The different cycle lengths create evolving patterns.

Gate Length (Pulse Width)

Pulse Width controls how long each gate stays high:

• Short (10-25%): Staccato, percussive triggers
• Medium (50%): Standard gate length
• Long (75-99%): Legato, overlapping notes

[Clock] (Pulse Width: 75%) ──> [ADSR Gate]

Longer gates give envelopes more time in the sustain phase.

Run/Stop Control

Use the Run input or button to start/stop:

[Toggle Button] ──> [Clock Run]

When stopped, clock outputs go low. When restarted, timing resumes (use Reset for consistent restart position).

Building Patterns

4-on-the-Floor

[Clock 1/4] ──> [Kick Trigger]

Basic Rock Beat

[Clock 1/4] ──> [Kick] (beats 1, 3)
[Clock 1/4] ──> [Snare] (beats 2, 4 - offset)
[Clock 1/8] ──> [Hi-Hat]

Driving Sequence

[Clock 1/16] ──> [Sequencer Clock]
[Clock 1/1] ──> [Sequencer Reset]

Ambient Pulses

[Clock 1/2] ──> [Envelope Gate]
(BPM: 40-60)

Connection Examples

Complete Rhythm Section

[Clock] ──1/4──> [Kick ADSR]
        ──1/8──> [Sequencer] ──> [Bass Oscillator]
        ──1/16──> [Hi-Hat ADSR]
        ──1/1──> [Sequencer Reset]

Synced Modulation

[Clock] ──1/4──> [LFO Sync]
        ──1/8──> [Sample & Hold Trigger]

Polymetric Setup

[Clock 1/8] ──> [Sequencer A (8 steps)]
            ──> [Sequencer B (6 steps)]
            ──> [Sequencer C (5 steps)]

Tips for Tight Timing

1. Use Reset: Always reset when starting to ensure all modules are synchronized
2. Match Pulse Widths: If modules expect specific gate lengths, adjust Pulse Width
3. Consider Latency: Audio processing has some latency; very fast divisions may drift
4. External Sync: For critical timing with other gear, use external clock from your DAW

Related Modules

• Sequencer - Primary clock destination
• ADSR Envelope - Gate inputs for rhythmic envelopes
• LFO - Sync input for tempo-locked modulation
• Sample & Hold - Clock-triggered sampling

VCA

Module ID: util.vca Category: Utilities Header Color: Yellow

The VCA module

Description

The Voltage Controlled Amplifier (VCA) controls the amplitude (volume) of a signal based on a control voltage input. It's an essential building block that allows envelopes, LFOs, and other control signals to shape the dynamics of your sound.

Despite the name suggesting audio use only, VCAs can process any signal type—they're equally useful for controlling the amount of modulation in a patch.

Inputs

Outputs

Parameters

How It Works

The VCA multiplies the input signal by the CV value:

Output = Input × CV × Level

• CV = 0: Output is silent (signal × 0)
• CV = 0.5: Output at half amplitude
• CV = 1: Output at full amplitude (determined by Level knob)

Linear vs Exponential Response

Linear:

• Direct relationship: double the CV, double the volume
• Best for tremolo and amplitude modulation
• Used for CV processing

Exponential:

• Matches human perception of loudness
• Small CV changes are subtle, large changes are dramatic
• Best for envelope-controlled volume (most common use)

Usage Tips

Basic Envelope Control

The most common VCA use—shaping volume with an envelope:

[Keyboard] ──Gate──> [ADSR] ──> [VCA CV]
[Oscillator] ──> [VCA Input] ──> [Output]

When you press a key:

1. Gate triggers the envelope
2. Envelope shapes the CV
3. VCA lets sound through based on envelope level

Without a VCA (or with CV always at 1), the oscillator would drone continuously.

Tremolo

Use an LFO for rhythmic volume variation:

[LFO] ──> [VCA CV]
[Oscillator] ──> [VCA Input] ──> [Output]

• Rate: 4-8 Hz for classic tremolo
• Response: Linear for more pronounced effect
• The sound pulses in volume with the LFO rhythm

Modulation Amount Control

Use a VCA to control how much modulation reaches a destination:

[LFO] ──> [VCA Input]
[Envelope] ──> [VCA CV]
[VCA Output] ──> [Filter Cutoff]

This creates modulation that fades in/out with the envelope—the filter wobble increases as the note develops.

Manual Level Control

Without CV connected, the Level knob acts as a simple volume control:

[Signal] ──> [VCA] ──> [Mixer]
             (Level: 0.7)

Ducking/Sidechain

Create pumping effects by using an inverted envelope:

[Kick Trigger] ──> [ADSR] ──> [Attenuverter (inverted)] ──> [VCA CV]
[Pad] ──> [VCA Input] ──> [Output]

When the kick hits, the pad ducks down, then rises back up.

Ring Modulation

At audio-rate CV, VCA becomes a ring modulator:

[Oscillator 1] ──> [VCA Input]
[Oscillator 2] ──> [VCA CV]
[VCA Output] ──> [Output]

This creates sum and difference frequencies—metallic, bell-like tones.

CV Crossfading

Use a VCA to fade between two signals:

[Signal A] ──> [VCA 1 Input]
[Signal B] ──> [VCA 2 Input]
[Crossfade CV] ──> [VCA 1 CV]
[Inverted Crossfade CV] ──> [VCA 2 CV]
[VCA 1 + VCA 2] ──> [Mixer] ──> [Output]

Velocity Sensitivity

Scale envelope output by MIDI velocity:

[MIDI Note Velocity] ──> [VCA CV]
[ADSR Output] ──> [VCA Input]
[VCA Output] ──> [Final VCA CV]

Harder key presses result in louder notes.

VCA Placement in Signal Chain

VCAs typically go near the end of the audio chain:

[Oscillator] ──> [Filter] ──> [VCA] ──> [Effects] ──> [Output]
                              ↑
                         [Envelope]

Why this order?

• Oscillator generates sound
• Filter shapes tone
• VCA controls volume
• Effects process the shaped sound

Connection Examples

Standard Synth Voice

[Oscillator] ──> [Filter] ──> [VCA] ──> [Output]
                    ↑            ↑
              [Envelope 1]  [Envelope 2]

Tremolo Effect

[Oscillator] ──> [Filter] ──> [VCA] ──> [Output]
                                 ↑
                              [LFO]

Modulation Depth Control

[LFO] ──> [VCA] ──> [Filter Cutoff CV]
            ↑
      [Mod Wheel]

Velocity-Sensitive Patch

[MIDI Velocity] ──> [VCA 1 CV]
[Envelope] ──> [VCA 1 Input]
[VCA 1 Output] ──> [VCA 2 CV]
[Oscillator] ──> [Filter] ──> [VCA 2] ──> [Output]

Tips

1. Always use a VCA for envelope-controlled sounds—it's what turns a drone into a playable note
2. Exponential response sounds more natural for volume changes
3. Linear response is better for AM/tremolo effects
4. Chain VCAs for complex amplitude control
5. Use the Level knob to balance signals in your patch

Related Modules

• ADSR Envelope - Primary CV source for VCA
• LFO - Tremolo modulation source
• Mixer - Combine multiple VCA outputs
• Attenuverter - Scale CV before VCA

Mixer

Module ID: util.mixer Category: Utilities Header Color: Yellow

The Mixer module

Description

The Mixer combines multiple audio or control signals into a single output. This 2-channel mixer allows you to blend signals with independent level control for each channel, plus a master output level.

Mixers are essential for:

• Combining multiple oscillators
• Blending modulation sources
• Creating submixes before effects
• Layering sounds

Inputs

Outputs

Parameters

How It Works

The mixer sums the inputs after applying their respective levels:

Mix = (Ch1 × Ch1Level + Ch2 × Ch2Level) × Master

Important: Summing two full-scale signals can exceed the -1 to +1 range. Use the channel levels to prevent clipping, or rely on the output module's limiter.

Usage Tips

Combining Oscillators

Create a richer sound by mixing multiple oscillators:

[Oscillator 1 (Saw)] ──> [Mixer Ch 1]
[Oscillator 2 (Square)] ──> [Mixer Ch 2]
[Mixer] ──> [Filter] ──> [VCA] ──> [Output]

• Detune oscillators slightly for thickness
• Use different waveforms for complexity
• Adjust levels to taste

Detuned Unison

Classic "supersaw" technique:

[Osc 1 (Detune: 0)] ──> [Mixer Ch 1]
[Osc 2 (Detune: +7 cents)] ──> [Mixer Ch 2]

The slight pitch difference creates a chorusing effect.

Octave Layering

Add harmonic richness:

[Osc 1 (C3)] ──> [Mixer Ch 1]
[Osc 2 (C4, octave up)] ──> [Mixer Ch 2] (Level: 0.5)

Lower the higher octave to keep the fundamental prominent.

Blending Modulation

Combine modulation sources:

[LFO (slow)] ──> [Mixer Ch 1]
[Envelope] ──> [Mixer Ch 2]
[Mixer] ──> [Filter Cutoff CV]

The filter responds to both the cyclic LFO and the triggered envelope.

Wet/Dry Effect Blend

Mix processed and original signals:

[Audio] ──> [Effect Input]
        ──> [Mixer Ch 1] (Dry)
[Effect Output] ──> [Mixer Ch 2] (Wet)
[Mixer] ──> [Output]

Adjust channel levels to control effect intensity.

Audio + Sub-Oscillator

Add weight with a sub-bass:

[Main Osc (Saw)] ──> [Mixer Ch 1]
[Sub Osc (Sine, -1 octave)] ──> [Mixer Ch 2] (Level: 0.6)

Chaining Mixers

Need more than 2 channels? Chain mixers:

[Osc 1] ──> [Mixer A Ch 1]
[Osc 2] ──> [Mixer A Ch 2]
[Mixer A] ──> [Mixer B Ch 1]
[Osc 3] ──> [Mixer B Ch 2]
[Mixer B] ──> [Output]

Or use multiple mixers into a final mixer.

Level Staging

Manage levels to avoid clipping:

1. Set individual channel levels to ~0.7 each
2. Adjust Master to compensate
3. Watch output levels (use Oscilloscope if needed)

Crossfading

Create a crossfade with complementary levels:

Ch 1 Level: 1.0 → 0.0
Ch 2 Level: 0.0 → 1.0

As one fades out, the other fades in. Automate with an LFO or envelope.

Connection Examples

Dual Oscillator Synth

[Keyboard V/Oct] ──> [Osc 1 V/Oct]
                 ──> [Osc 2 V/Oct]
[Osc 1] ──> [Mixer Ch 1]
[Osc 2] ──> [Mixer Ch 2]
[Mixer] ──> [Filter] ──> [VCA] ──> [Output]

Parallel Modulation

[LFO] ──> [Mixer Ch 1]
[Random/S&H] ──> [Mixer Ch 2]
[Mixer] ──> [Parameter CV]

Submix for Effects

[Lead Synth] ──> [Mixer Ch 1]
[Pad Synth] ──> [Mixer Ch 2]
[Mixer] ──> [Reverb] ──> [Output]

Gain Staging Tips

Audio vs Control Signals

The mixer works with both audio and control signals:

Audio Mixing:

• Combines waveforms
• Creates complex timbres
• Watch for clipping

Control Mixing:

• Combines modulation sources
• Creates complex modulation shapes
• No clipping concerns (but consider destination range)

Related Modules

• Oscillator - Primary signals to mix
• VCA - Level control for individual sources
• Attenuverter - Scale signals before mixing
• Audio Output - Final destination with metering

Attenuverter

Module ID: util.attenuverter Category: Utilities Header Color: Yellow

The Attenuverter module

Description

The Attenuverter is a utility module that scales, inverts, and offsets signals. The name combines "attenuate" (reduce) and "invert" (flip). It's an essential tool for adapting modulation signals to fit the needs of your destination parameters.

Key functions:

• Reduce signal strength (attenuation)
• Flip signal polarity (inversion)
• Shift signal baseline (offset)

Inputs

Outputs

Parameters

How It Works

The attenuverter applies this formula:

Output = (Input × Amount) + Offset

Amount Knob

• +1.0: Full positive (signal unchanged)
• +0.5: Half strength
• 0.0: Signal canceled (only offset remains)
• -0.5: Half strength, inverted
• -1.0: Full negative (signal inverted)

Offset Knob

Adds a constant value to shift the signal:

• +0.5: Shifts signal up by 0.5
• 0.0: No shift
• -0.5: Shifts signal down by 0.5

Usage Tips

Reducing Modulation Depth

An LFO may be too strong for subtle vibrato:

[LFO] ──> [Attenuverter] ──> [Oscillator FM]
           (Amount: 0.2)

Only 20% of the LFO reaches the oscillator.

Inverting Modulation

Flip the direction of modulation:

[Envelope] ──> [Attenuverter] ──> [Filter Cutoff CV]
                (Amount: -1.0)

Instead of the filter opening on attack, it closes.

Converting Unipolar to Bipolar

An envelope (0 to 1) needs to swing both ways:

[Envelope] ──> [Attenuverter] ──> [Pitch CV]
                (Amount: 2.0, Offset: -1.0)

• Original: 0 to 1
• After: -1 to +1 (centered around zero)

Converting Bipolar to Unipolar

An LFO (-1 to +1) needs to stay positive:

[LFO] ──> [Attenuverter] ──> [CV Destination]
           (Amount: 0.5, Offset: 0.5)

• Original: -1 to +1
• After: 0 to 1

Creating a Fixed Voltage

With no input connected, the offset becomes a constant:

[Attenuverter] ──> [Parameter CV]
(Input: none, Offset: 0.7)

Outputs constant 0.7—useful for manual CV sources.

Scaling for Range Matching

Match an envelope's range to a parameter:

[Envelope (0-1)] ──> [Attenuverter] ──> [Filter Cutoff]
                      (Amount: 0.6, Offset: 0.2)

• Output ranges from 0.2 to 0.8
• Never fully closed, never fully open

Ducking/Sidechain Effect

Invert an envelope for ducking:

[Kick Gate] ──> [Envelope] ──> [Attenuverter] ──> [Pad VCA CV]
                                (Amount: -1.0, Offset: 1.0)

• Kick hits → Envelope rises → Attenuverter inverts → Pad ducks
• Offset keeps pad at full volume when envelope is zero

Precise Modulation Amount

Many parameters don't have their own "modulation depth" control. Use attenuverter:

[LFO] ──> [Attenuverter (Amount: 0.3)] ──> [Filter Cutoff CV]

Now you have precise control over modulation depth.

Visual Understanding

Positive Amount

Input:  ╱╲╱╲╱╲   (LFO)
Output: ╱╲╱╲╱╲   (Same direction, possibly smaller)

Negative Amount (Inverted)

Input:  ╱╲╱╲╱╲
Output: ╲╱╲╱╲╱   (Flipped upside down)

With Offset

Input:  ╱╲╱╲╱╲   (Centered at 0)
Output: ¯╱╲╱╲╱╲¯ (Shifted up by offset)

Common Configurations

Connection Examples

Subtle Vibrato

[LFO] ──> [Attenuverter (0.1)] ──> [Osc FM]

Inverted Filter Envelope

[Envelope] ──> [Attenuverter (-0.8)] ──> [Filter CV]

Modulation Depth Control

[LFO] ──> [Attenuverter] ──> [Parameter]
              ↑
         [Mod Wheel] (controls Amount)

Creating Complex Modulation

[LFO 1] ──> [Attenuverter 1 (0.5)] ──┐
                                      ├──> [Mixer] ──> [Destination]
[LFO 2] ──> [Attenuverter 2 (-0.3)] ─┘

Tips

1. Start at 0: When patching new modulation, start Amount at 0 and slowly increase
2. Watch polarity: Some modulations sound better inverted
3. Use offset for bias: Shift the modulation center to taste
4. Chain if needed: Multiple attenuverters can create complex scaling

Related Modules

• LFO - Common source to attenuate
• ADSR Envelope - Common source to scale/invert
• Mixer - Combine after scaling
• VCA - Alternative way to control signal strength

Sample & Hold

Module ID: util.samplehold Category: Utilities Header Color: Yellow

The Sample & Hold module

Description

The Sample & Hold (S&H) module captures the instantaneous value of an input signal when triggered, then holds that value constant until the next trigger. This creates stepped, staircase-like outputs from continuous signals.

Classic uses:

• Random pitched sequences from noise
• Stepped modulation from LFOs
• Quantized parameter changes
• Creating rhythmic variation

Inputs

Outputs

Parameters

How It Works

1. Input signal changes continuously
2. Trigger receives a rising edge (gate goes from 0 to 1)
3. Output instantly captures input value at that moment
4. Output holds steady until next trigger
5. Repeat

Input:   ~~~∿∿~~~∿∿~~~  (continuous signal)
Trigger: _|‾|__|‾|__|‾   (pulses)
Output:  ____‾‾‾‾____‾‾  (stepped values)

Usage Tips

Random Notes from Noise

The classic S&H patch—random melodies:

[Noise] ──> [S&H Input]
[Clock] ──> [S&H Trigger]
[S&H Output] ──> [Oscillator V/Oct]

Each clock pulse picks a random voltage from the noise, creating random pitches.

Stepped LFO

Turn a smooth LFO into stepped modulation:

[LFO (Sine)] ──> [S&H Input]
[Clock (faster)] ──> [S&H Trigger]
[S&H Output] ──> [Filter Cutoff]

The filter cutoff moves in discrete steps rather than smoothly.

Rhythmic Variations

Sample a slow LFO at regular intervals:

[LFO (very slow)] ──> [S&H Input]
[Clock 1/4] ──> [S&H Trigger]
[S&H Output] ──> [Parameter]

Each beat has a different (but related) modulation value.

Track and Hold

Sample a melodic sequence to create variations:

[Sequencer CV] ──> [S&H Input]
[Random Trigger] ──> [S&H Trigger]
[S&H Output] ──> [Another Oscillator V/Oct]

The second oscillator plays held notes from the sequence.

Slew for Portamento

Use the Slew parameter to smooth transitions:

[Noise] ──> [S&H] ──> [Osc V/Oct]
             (Slew: 100ms)

Instead of instant pitch jumps, notes glide to each new value.

Quantized Random

For random notes that stay in key, add a quantizer after S&H:

[Noise] ──> [S&H] ──> [Quantizer] ──> [Osc V/Oct]

(Requires a quantizer module)

Stutter Effect

Sample audio at regular intervals:

[Audio] ──> [S&H Input]
[Fast Clock] ──> [S&H Trigger]
[S&H Output] ──> [Output]

Creates a bit-crusher/sample-rate-reduction effect.

Probability-Based Changes

Use a randomly triggered S&H:

[Random Gate (probability)] ──> [S&H Trigger]
[Parameter Source] ──> [S&H Input]

The parameter only changes when the random gate fires.

Self-Patched Chaos

Feed S&H output back with modification:

[S&H Output] ──> [Attenuverter] ──> [S&H Input]
[Clock] ──> [S&H Trigger]

Creates chaotic, evolving patterns. Adjust attenuverter for different behaviors.

Slew Control

The Slew parameter adds portamento between held values:

With high slew values, the output may not reach the held value before the next trigger—creating even smoother movement.

Connection Examples

Random Arpeggio

[Noise] ──> [S&H] ──> [Quantizer] ──> [Osc V/Oct]
[Clock 1/16] ──> [S&H Trigger]

Generative Modulation

[LFO 1 (slow)] ──> [S&H] ──> [Filter Cutoff CV]
[LFO 2 (fast)] ──> [S&H Trigger]

Held Sequence Notes

[Sequencer] ──> [S&H] ──> [Second Voice]
[Random Gate] ──> [S&H Trigger]

Bit Crusher

[Audio] ──> [S&H] ──> [Output]
[Clock (very fast)] ──> [S&H Trigger]

Sample Sources

Different inputs create different results:

Related Modules

• Clock - Trigger source for S&H
• LFO - Input source for stepped modulation
• Sequencer - Alternative way to create stepped sequences
• Attenuverter - Scale S&H output

Sequencer

Module ID: util.sequencer Category: Utilities Header Color: Yellow

The Sequencer module

Description

The 16-Step Sequencer generates programmable CV and gate patterns that cycle through a sequence of values. It's the heart of pattern-based music, outputting melodies, rhythms, and modulation sequences.

Each step can have:

• A CV value (for pitch, modulation, etc.)
• A gate on/off state (for triggering)
• Adjustable length (1-16 active steps)

Inputs

Outputs

Parameters

How It Works

1. Clock input advances to the next step
2. CV output immediately changes to new step's value
3. Gate output goes high if step's gate is on
4. Gate goes low before next clock (based on gate length)
5. At end of sequence (length reached), EOC pulses and sequence restarts

Usage Tips

Basic Melody Sequencing

Create a simple melodic pattern:

[Clock 1/8] ──> [Sequencer Clock]
[Sequencer CV] ──> [Oscillator V/Oct]
[Sequencer Gate] ──> [ADSR Gate]

1. Set step CV values for your melody
2. Toggle gates on for notes, off for rests
3. Adjust length for pattern size

Programming Pitches

CV values map to pitch:

• 0.0 = Base note
• 0.083 = +1 semitone
• 0.167 = +2 semitones
• 0.5 = +6 semitones (tritone)
• 1.0 = +1 octave

For a C major scale pattern:

Rhythmic Patterns

Use gates for rhythm:

Step:  1  2  3  4  5  6  7  8
Gate:  ●  ○  ●  ○  ●  ●  ○  ●

(● = on, ○ = off)

This creates a syncopated pattern.

Modulation Sequences

Use CV output for parameter modulation:

[Sequencer CV] ──> [Filter Cutoff CV]

Each step changes the filter cutoff, creating rhythmic timbral variation.

Direction Modes

Forward: 1 → 2 → 3 → ... → 16 → 1 → ...

Backward: 16 → 15 → 14 → ... → 1 → 16 → ...

Pendulum: 1 → 2 → ... → 16 → 15 → ... → 1 → ...

Random: Jumps to random step each clock

Using Reset

Sync sequences to song sections:

[Master Clock 1/1 (bar)] ──> [Sequencer Reset]
[Master Clock 1/16] ──> [Sequencer Clock]

Sequence resets every bar, keeping it locked to the downbeat.

EOC for Chaining

Use End of Cycle to trigger events:

[Sequencer A EOC] ──> [Sequencer B Reset]

Sequencer B resets when A completes a cycle.

Variable Length Patterns

Set length shorter than 16 for odd meters:

• Length 3: Creates waltz/triplet feel
• Length 5: Creates 5/8 time
• Length 7: Creates 7/8 time
• Length 12: Swing/shuffle patterns

Polyrhythms

Run two sequencers at the same clock with different lengths:

[Clock] ──> [Seq A (Length: 4)] ──> [Osc 1]
        ──> [Seq B (Length: 3)] ──> [Osc 2]

4 against 3 creates evolving polyrhythmic patterns.

Ratcheting

Clock the sequencer faster for a step by using clock multiplication or additional triggers.

CV and Gate Independence

CV and Gate don't have to move together:

[Fast Clock] ──> [Sequencer Clock] ──> [CV to Modulation]
[Slow Clock] ──> [Envelope Gate] (separate rhythm)

Building Sequences

Bassline (8 steps)

Arpeggio (4 steps)

Filter Sequence (8 steps)

Connection Examples

Complete Bass Voice

[Clock 1/8] ──> [Sequencer Clock]
[Clock 1/1] ──> [Sequencer Reset]
[Sequencer CV] ──> [Oscillator V/Oct]
[Sequencer Gate] ──> [ADSR Gate]
[Oscillator] ──> [Filter] ──> [VCA] ──> [Output]

Polymetric Setup

[Clock] ──> [Seq A (7 steps)] ──> [Voice 1]
        ──> [Seq B (5 steps)] ──> [Voice 2]

Modulation Sequencing

[Slow Clock] ──> [Sequencer]
[Seq CV] ──> [Attenuverter] ──> [Filter Cutoff]
[Seq CV] ──> [Attenuverter] ──> [Resonance]

Tips

1. Start simple: Begin with 4-step patterns and expand
2. Use rests: Gates off create space in the rhythm
3. Vary length: Odd lengths create interesting cycles
4. Reset strategically: Keep sequences locked to musical sections
5. Layer sequences: Multiple sequences at different rates create complexity

Related Modules

• Clock - Timing source for sequencer
• Oscillator - CV destination for melody
• ADSR Envelope - Gate destination for note shaping
• Sample & Hold - Alternative for random sequences

Delay

Module ID: fx.delay Category: Effects Header Color: Purple

The Delay module

Description

The Stereo Delay creates echoes and rhythmic repetitions by playing back a delayed copy of the input signal. It features independent left and right delay times, feedback for multiple echoes, and filtering to shape the delay character.

Delays are essential for:

• Adding depth and space
• Creating rhythmic patterns
• Doubling and thickening sounds
• Ambient and experimental textures

Inputs

Outputs

Parameters

How It Works

1. Input signal enters the delay buffer
2. A delayed copy is played back after the set time
3. This output is mixed with dry signal
4. Feedback routes output back to input for multiple echoes
5. Filters shape each repetition

Feedback Behavior

• 0%: Single echo, no repetitions
• 30%: Several echoes, natural decay
• 50%: Many echoes, sustained
• 70%+: Long trails, approaching self-oscillation
• 95%: Near-infinite repeats (careful!)

Ping Pong Mode

When enabled, echoes alternate between left and right channels:

L: Sound → (silence) → Echo → (silence) → Echo...
R: (silence) → Echo → (silence) → Echo → ...

Creates wide stereo movement.

Usage Tips

Basic Slapback

Short delay for doubling/thickening:

Time L: 80 ms
Time R: 100 ms
Feedback: 0
Mix: 0.3

Adds thickness without obvious echoes.

Rhythmic Delay

Sync to tempo for musical echoes:

Time L: 375 ms (1/8 note at 120 BPM)
Time R: 750 ms (1/4 note)
Feedback: 0.4
Ping Pong: On

Echoes fall on the beat.

Tape Delay Simulation

Warm, vintage-style delay:

Feedback: 0.5
HP Filter: 200 Hz
LP Filter: 4000 Hz

The filters remove highs and lows with each repeat, simulating tape degradation.

Dub Delay

Dark, spacious echoes:

Time: Long (600-1000 ms)
Feedback: 0.6
LP Filter: 2000 Hz

Low-passed feedback creates dark, dubbed-out echoes.

Tempo Sync

With a clock connected and Sync enabled, Time knobs select musical divisions:

Dotted Note Delays

For the classic U2/Edge sound, use dotted eighth notes:

Time: 1/8 dotted (375 ms at 120 BPM)
Feedback: 0.4
Mix: 0.5

Modulated Delay (Chorus-like)

Apply slow LFO to Time CV:

[LFO (0.5 Hz)] ──> [Delay Time CV]

The varying delay time creates pitch modulation effects.

Self-Oscillation

At high feedback (90%+), the delay can self-oscillate:

1. Send a sound through the delay
2. Turn feedback up high
3. Remove input
4. The delay continues generating sound

Use filters to control the character of oscillation.

Sidechain-Pumping Delay

Modulate feedback with an envelope:

[Kick Gate] ──> [Envelope] ──> [Inverted] ──> [Feedback CV]

Feedback ducks on each kick, creating pumping echoes.

Delay Time Reference

Formula: 60000 / BPM = quarter note in ms

Connection Examples

Standard Insert

[Synth] ──> [Delay Left In]
[Delay Left Out] ──> [Output Left]
[Delay Right Out] ──> [Output Right]

Send/Return

[Mixer Send] ──> [Delay]
[Delay] ──> [Mixer Return]
(Mix: 100% wet)

Tempo-Synced

[Clock] ──> [Delay Sync]
[Synth] ──> [Delay] ──> [Output]

Modulated Delay

[LFO] ──> [Delay Time CV]
[Audio] ──> [Delay] ──> [Output]

Sound Design Tips

Related Modules

• Reverb - For ambient space
• Chorus - For thickening without echoes
• Clock - For tempo sync
• LFO - For time modulation

Reverb

Module ID: fx.reverb Category: Effects Header Color: Purple

The Reverb module

Description

The Reverb simulates acoustic spaces by creating a dense wash of reflections that decay over time. From small rooms to vast halls, reverb places your sounds in a virtual environment and adds depth, dimension, and atmosphere.

Inputs

Outputs

Parameters

Parameter Deep Dive

Decay Time

How long the reverb tail lasts:

Pre-Delay

Gap between dry signal and reverb onset:

• 0-10 ms: Reverb starts immediately, sound feels close
• 20-40 ms: Natural separation, clear attack
• 50-100 ms: Distinct echo before reverb, adds depth
• 100+ ms: Noticeable gap, special effect

Pre-delay helps maintain clarity—the attack of sounds comes through before reverb.

Size

Affects the density and character of reflections:

• Small (0.1-0.3): Dense, colored reflections
• Medium (0.4-0.6): Balanced, natural
• Large (0.7-1.0): Sparse, spacious reflections

Damping

Simulates absorption of high frequencies by surfaces:

• Low (0.0-0.3): Bright, reflective surfaces (tile, glass)
• Medium (0.4-0.6): Balanced, natural decay
• High (0.7-1.0): Dark, absorbed sound (carpet, curtains)

Higher damping = darker reverb that's easier to mix.

Width

Controls stereo spread:

• 0.0: Mono reverb (centered)
• 0.5: Moderate stereo spread
• 1.0: Full stereo width

Usage Tips

Vocal Reverb

Clear, present vocals:

Decay: 1.5 s
Pre-Delay: 40 ms
Size: 0.5
Damping: 0.6
Mix: 0.2

Pre-delay separates the vocal from reverb; damping prevents harshness.

Drums/Percussion

Tight, punchy room:

Decay: 0.5 s
Pre-Delay: 10 ms
Size: 0.3
Damping: 0.5
Mix: 0.25

Short decay keeps rhythm tight.

Synth Pad

Lush, expansive atmosphere:

Decay: 4.0 s
Pre-Delay: 50 ms
Size: 0.8
Damping: 0.4
Mix: 0.5

Long decay and large size create immersive space.

Ambient/Experimental

Infinite shimmer:

Decay: 15+ s
Pre-Delay: 100 ms
Size: 1.0
Damping: 0.3 (bright)
Mix: 0.7

Creates evolving, self-sustaining textures.

Gated Reverb

80s drum sound (requires gate module):

[Drums] ──> [Reverb] ──> [Gate] ──> [Output]
           Decay: 3s    Threshold: 0.3
           Mix: 100%    Attack: 0ms
                        Hold: 200ms
                        Release: 50ms

Reverb is cut short by gate for dramatic effect.

Send/Return Setup

Process multiple sources through one reverb:

[Synth 1] ──(send)──┐
[Synth 2] ──(send)──┼──> [Reverb (Mix: 100%)] ──> [Return Mixer]
[Drums]   ──(send)──┘

More efficient and creates cohesive space.

Decay Modulation

Evolving reverb character:

[LFO (slow)] ──> [Reverb Decay CV]

Reverb time breathes and changes over time.

Spring Reverb Character

For vintage spring-like sound:

Size: 0.2 (small)
Decay: 1.5 s
Pre-Delay: 0 ms
Damping: 0.3

Small size creates metallic, sproingy character.

Plate Reverb Character

Classic studio plate:

Size: 0.5
Decay: 2.0 s
Pre-Delay: 0 ms
Damping: 0.4
Width: 1.0

Dense, smooth decay.

Mix Positioning

Reverb level affects perceived distance:

Connection Examples

Insert Effect

[Synth] ──> [Reverb] ──> [Output]

Send/Return

[Mixer] ──Send──> [Reverb (Mix: 100%)]
[Reverb] ──Return──> [Mixer]

Reverb into Delay

[Audio] ──> [Reverb] ──> [Delay] ──> [Output]

Creates rhythmic echoes of the reverb tail.

Sidechain Reverb

[Audio] ──> [Reverb] ──> [VCA] ──> [Output]
[Audio] ──> [Envelope Follower] ──> [Inverted] ──> [VCA CV]

Reverb ducks when dry signal is present.

Space Presets

Related Modules

• Delay - Discrete echoes vs diffuse reverb
• Chorus - Thickening without space
• EQ - Shape reverb tone
• VCA - Control reverb level dynamically

Chorus

Module ID: fx.chorus Category: Effects Header Color: Purple

The Chorus module

Description

The Chorus effect creates a thicker, richer sound by layering slightly detuned and delayed copies of the input signal. It simulates the natural variation when multiple performers play the same part, adding warmth and movement without obvious echoes.

Inputs

Outputs

Parameters

How It Works

1. Input signal is copied to multiple delay lines
2. Each delay line has slightly different base delay
3. An internal LFO modulates each delay time
4. The varying delays create pitch shifts and phase differences
5. Mixed together, this creates the characteristic "ensemble" sound

The Chorus Sound

The effect creates subtle beating and pitch variation:

• Slow rate: Gentle swaying, lush
• Fast rate: Vibrato-like, more intense
• Light depth: Subtle thickening
• Heavy depth: Dramatic wobble, almost out of tune

Usage Tips

Classic Analog Chorus

Warm, vintage sound:

Rate: 0.5 Hz
Depth: 0.4
Delay: 8 ms
Voices: 2
Mix: 0.5

Subtle Thickening

Barely perceptible but adds depth:

Rate: 0.3 Hz
Depth: 0.2
Delay: 5 ms
Mix: 0.3

Good for vocals and solo instruments.

Lush Ensemble

Rich, string-machine style:

Rate: 0.8 Hz
Depth: 0.6
Delay: 15 ms
Voices: 4
Stereo: 1.0
Mix: 0.6

Creates wide, dreamy textures.

Bass Chorus

Keep low end intact:

Rate: 0.4 Hz
Depth: 0.3
Delay: 10 ms
Mix: 0.4

Lighter settings prevent the bass from getting muddy.

Vibrato Mode

Extreme settings for pitch wobble:

Rate: 4 Hz
Depth: 0.8
Mix: 1.0 (100% wet)

At full wet, you hear only the modulated signal—pure vibrato.

Leslie Speaker Simulation

For organ-like rotation:

Rate: Slow: 0.7 Hz / Fast: 6 Hz (modulate via Rate CV)
Depth: 0.7
Voices: 2
Stereo: 1.0

Switch between slow and fast for classic organ effect.

Stereo Width Enhancement

Use chorus to widen a mono source:

[Mono Signal] ──> [Chorus] ──> [Stereo Output]
                  Stereo: 1.0
                  Mix: 0.4

The phase differences create stereo spread.

Clean Guitar Chorus

Classic '80s clean tone:

Rate: 0.6 Hz
Depth: 0.5
Delay: 12 ms
Voices: 2
Mix: 0.5

Synth Pad Enhancement

Make pads more interesting:

[Pad Oscillators] ──> [Chorus] ──> [Reverb] ──> [Output]
                      Rate: 0.4 Hz
                      Depth: 0.5
                      Voices: 4

The chorus adds movement before reverb smears it together.

Modulating Rate

Create evolving chorus textures:

[LFO (very slow)] ──> [Chorus Rate CV]

The chorus speed itself changes over time.

Voice Count Effects

More voices = thicker but potentially muddier sound.

Delay Time Effects

Connection Examples

Basic Insert

[Synth] ──> [Chorus] ──> [Output]

In Effects Chain

[Synth] ──> [Chorus] ──> [Delay] ──> [Reverb] ──> [Output]

Chorus before time-based effects is typical.

Parallel Chorus

[Signal] ──> [Mixer Ch 1 (dry)]
         ──> [Chorus] ──> [Mixer Ch 2 (wet)]
         [Mixer] ──> [Output]

Blend dry and chorused signals independently.

Modulated Ensemble

[LFO 1 (slow)] ──> [Chorus Rate CV]
[LFO 2] ──> [Chorus Depth CV]
[Synth] ──> [Chorus] ──> [Output]

Chorus vs Similar Effects

Tips

1. Less is more: Subtle chorus often works better than heavy
2. Watch the bass: Heavy chorus can muddy low frequencies
3. Use stereo: Chorus really shines in stereo
4. Stack effects: Chorus into reverb is magical
5. Try extreme settings: 100% wet creates interesting vibratos

Related Modules

• Delay - For longer echo effects
• Reverb - Combine for ambient textures
• LFO - For rate modulation
• Oscillator - PWM creates similar thickening

Distortion

Module ID: fx.distortion Category: Effects Header Color: Purple

The Distortion module

Description

The Distortion module adds harmonic richness and grit by clipping, saturating, or folding the input signal. From subtle warmth to aggressive destruction, distortion shapes the character of sounds and adds presence.

Inputs

Outputs

Parameters

Distortion Types

Soft Clip

Gentle saturation that rounds off peaks:

• Adds warm, even harmonics
• Tube/tape-like character
• Compresses dynamics naturally
• Good for subtle warmth

Hard Clip

Aggressive clipping that chops off peaks:

• Adds harsh, odd harmonics
• Transistor/digital character
• More aggressive, buzzy sound
• Classic overdrive/fuzz

Fold

Wave folding that reflects the signal back:

• Complex harmonic content
• Synth-like, metallic character
• Creates additional partials
• West Coast synthesis style

Bit Crush

Reduces bit depth for lo-fi character:

• Introduces quantization noise
• Gritty, digital degradation
• 8-bit/vintage sampler sound
• Adds "crunchy" character

Usage Tips

Subtle Warmth

Add life to sterile digital signals:

Type: Soft
Drive: 0.2
Mix: 0.5

Just a hint of saturation, barely noticeable but adds presence.

Bass Overdrive

Add harmonics that cut through the mix:

Type: Soft
Drive: 0.4
Tone: 2000 Hz
Mix: 0.7

The tone filter prevents harsh high frequencies while preserving grind.

Aggressive Lead

In-your-face distortion:

Type: Hard
Drive: 0.8
Tone: 4000 Hz
Mix: 1.0

Lo-Fi Texture

Vintage sampler vibes:

Type: Bit
Drive: 0.6
Mix: 0.8

Synth Processing

Add complex harmonics to simple waveforms:

[Sine Oscillator] ──> [Distortion (Fold)] ──> [Filter] ──> [Output]
                      Drive: 0.5

Wave folding turns a simple sine into a complex tone.

Drum Processing

Add punch and presence:

Type: Soft
Drive: 0.3
Tone: 6000 Hz
Mix: 0.6

Parallel Distortion

Keep clean low end, distort highs:

[Input] ──> [High Pass] ──> [Distortion] ──> [Mixer Ch 2]
        ──> [Low Pass] ────────────────────> [Mixer Ch 1]
[Mixer] ──> [Output]

The clean bass stays tight while harmonics are added to mids/highs.

Modulated Drive

Dynamic distortion amount:

[Envelope] ──> [Distortion Drive CV]

More distortion during attack, cleaner during sustain.

Creative Textures

Use wave folding for synth-like sounds:

[LFO] ──> [Attenuverter] ──> [Distortion (Fold)] ──> [Filter]

Even slow control signals become complex audio when folded.

Drive Amount Guide

Tone Control

The Tone knob is a low-pass filter on the output:

Distortion creates high harmonics—use Tone to control harshness.

Connection Examples

Standard Insert

[Synth] ──> [Distortion] ──> [Filter] ──> [VCA] ──> [Output]

Post-Filter Distortion

[Oscillator] ──> [Filter] ──> [Distortion] ──> [VCA] ──> [Output]

Different character—filter first can prevent extreme harshness.

Send Effect

[Mixer Send] ──> [Distortion (Mix: 100%)] ──> [Mixer Return]

Blend clean and distorted in the mixer.

Dynamic Distortion

[Input] ──> [Distortion]
[Input] ──> [Envelope Follower] ──> [Distortion Drive CV]

Louder input = more distortion.

Distortion in the Signal Chain

Before Filter: Maximum harmonics, filter can tame harshness After Filter: Cleaner distortion, filter cutoff is clean Before VCA: Consistent distortion amount After VCA: Distortion varies with dynamics

Most common: Oscillator → Filter → Distortion → VCA

Tips

1. Use output compensation: Distortion can increase level significantly
2. Consider the Tone knob: Bright distortion can be harsh
3. Try different orders: Filter → Distortion vs Distortion → Filter
4. Don't overdo it: Subtlety often works better in a mix
5. Watch your ears: High-frequency distortion can be fatiguing

Related Modules

• SVF Filter - Shape distortion harmonics
• Compressor - Control dynamics before/after
• EQ - Fine-tune distortion character
• VCA - Control distortion input level

EQ

Module ID: fx.eq Category: Effects Header Color: Purple

The EQ module

Description

The 3-Band Parametric EQ allows precise control over the frequency content of your signal. Each band can boost or cut a specific frequency range with adjustable center frequency and bandwidth (Q).

EQ is essential for:

• Shaping tone and timbre
• Fixing frequency problems
• Making sounds fit in a mix
• Creative sound design

Inputs

Outputs

Parameters

Low Band

Mid Band

High Band

Understanding EQ

Frequency Ranges

Q (Bandwidth)

Q controls how wide or narrow the affected frequency range is:

• Low Q (0.5-1.5): Wide, gentle curves, affects many frequencies
• Medium Q (2-4): Focused but still musical
• High Q (5-10): Surgical, narrow cuts, affects specific frequencies

Boost vs Cut

General rule: Cut narrow, boost wide

• Cuts are good for removing problem frequencies (use higher Q)
• Boosts add character but can sound unnatural (use lower Q)

Usage Tips

Removing Mud

Clean up muddy sounds:

Mid Freq: 300 Hz
Mid Gain: -3 to -6 dB
Mid Q: 2.0

This is the common "mud" frequency range.

Adding Warmth

Add body and warmth:

Low Freq: 100 Hz
Low Gain: +3 dB
Low Q: 1.0

Adding Presence

Make sounds cut through:

High Freq: 3 kHz
High Gain: +3 dB
High Q: 1.5

Telephone Effect

Dramatic filtering for effect:

Low Freq: 300 Hz, Gain: -12 dB
High Freq: 3 kHz, Gain: -12 dB

Cuts lows and highs, leaving only mids.

De-Boxing

Remove boxy sound from recordings:

Mid Freq: 400-600 Hz
Mid Gain: -3 dB
Mid Q: 2.5

Air and Sparkle

Add high-end shine:

High Freq: 12 kHz
High Gain: +2 dB
High Q: 0.7

Wide boost adds open, airy quality.

Finding Problem Frequencies

1. Set one band's Q to high (5.0+)
2. Boost the gain to +6 dB
3. Sweep the frequency while listening
4. When you hear the problem clearly, reduce gain to cut

Subtractive EQ

Start by cutting problem frequencies rather than boosting:

• Often sounds more natural
• Less likely to cause clipping
• Maintains headroom

Frequency Slot Carving

Give each sound its own space:

Bass: Boost 80 Hz, cut 300 Hz
Synth: Cut 80 Hz, boost 500 Hz
Lead: Cut 500 Hz, boost 2 kHz

Each element has its own frequency territory.

Frequency Cheat Sheet

Problem Frequencies

Enhancement Frequencies

Connection Examples

Channel Strip

[Sound] ──> [EQ] ──> [Compressor] ──> [Output]

Post-Effect Processing

[Synth] ──> [Distortion] ──> [EQ] ──> [Output]

EQ after distortion can tame harsh frequencies.

Reverb Shaping

[Sound] ──> [Reverb] ──> [EQ] ──> [Output]

Cut lows from reverb to prevent mud.

Tips

1. Cut before boost: Try cutting unwanted frequencies first
2. Less is more: Small EQ moves often sound best
3. Use your ears: Trust what sounds good, not what looks right
4. A/B test: Bypass the EQ to compare processed and original
5. Watch levels: Boosting increases overall level

Related Modules

• SVF Filter - Dramatic filtering
• Compressor - Dynamics after EQ
• Distortion - Harmonics to then EQ
• Reverb - Shape reverb tone with EQ

Compressor

Module ID: fx.compressor Category: Effects Header Color: Purple

The Compressor module

Description

The Compressor reduces the dynamic range of a signal by attenuating loud portions while leaving quiet portions unchanged. This creates a more consistent level, adds punch, and can create distinctive pumping effects.

Inputs

Outputs

Parameters

How It Works

1. Signal level is measured (or sidechain input if connected)
2. When level exceeds Threshold, compression begins
3. Ratio determines how much signals above threshold are reduced
4. Attack controls how fast compression responds to transients
5. Release controls how fast compression recovers
6. Makeup Gain compensates for level reduction

Understanding Ratio

• 1:1: No compression (bypass)
• 2:1: For every 2 dB above threshold, only 1 dB passes
• 4:1: For every 4 dB above threshold, only 1 dB passes
• 10:1: Heavy compression
• ∞:1: Limiting (nothing passes above threshold)

Threshold Example

If Threshold = -20 dB and Ratio = 4:1:

• Signal at -30 dB: Unchanged
• Signal at -20 dB: Unchanged (at threshold)
• Signal at -10 dB: Reduced to -17.5 dB

Usage Tips

Gentle Leveling

Smooth out dynamics without obvious compression:

Threshold: -18 dB
Ratio: 2:1
Attack: 20 ms
Release: 200 ms
Knee: Soft

Punchy Drums

Add snap and punch:

Threshold: -10 dB
Ratio: 4:1
Attack: 10 ms
Release: 50 ms

Fast attack catches transients, fast release lets energy through.

Sustained Bass

Even out bass levels:

Threshold: -15 dB
Ratio: 4:1
Attack: 5 ms
Release: 150 ms

Vocal Compression

Consistent vocal level:

Threshold: -20 dB
Ratio: 3:1
Attack: 10 ms
Release: 100 ms
Knee: Soft

Synth Pad Sustain

Make pads sustain more evenly:

Threshold: -24 dB
Ratio: 3:1
Attack: 30 ms
Release: 300 ms

Slow attack preserves natural swell.

Sidechain Pumping

Classic EDM pumping effect:

[Kick] ──> [Compressor Sidechain]
[Pad/Bass] ──> [Compressor Input]

Threshold: -30 dB
Ratio: 6:1
Attack: 1 ms
Release: 200 ms

The kick ducks the pad, creating rhythmic pumping.

Peak Limiting

Catch peaks without obvious compression:

Threshold: -3 dB
Ratio: 10:1 or higher
Attack: 0.1 ms
Release: 50 ms

Parallel Compression

Blend compressed and dry signals:

[Input] ──> [Compressor] ──> [Mixer Ch 2]
        ──> [Mixer Ch 1 (dry)]
[Mixer] ──> [Output]

Heavy compression (6:1+) on the compressed path, blend to taste.

Using Gain Reduction Output

Visualize or control other parameters based on compression:

[Compressor GR Output] ──> [Other Parameter CV]

Could modulate filter cutoff, pan, effects send, etc.

Attack and Release Guide

Attack Times

Release Times

Knee Types

Hard Knee

Compression applies suddenly at threshold. More obvious compression, more aggressive.

Soft Knee

Compression gradually increases around threshold. More transparent, natural sound.

Gain Staging

1. Set Threshold to catch peaks you want to compress
2. Adjust Ratio for desired amount
3. Use Makeup Gain to match bypassed level
4. A/B compare with bypass to verify

Connection Examples

Channel Strip

[Synth] ──> [EQ] ──> [Compressor] ──> [Output]

Sidechain Setup

[Kick] ──> [Compressor Sidechain]
[Bass] ──> [Compressor Input]
[Compressor Output] ──> [Output]

Parallel Compression

[Drums] ──> [Compressor (heavy)] ──> [Mixer (wet)]
        ──> [Mixer (dry)]
[Mixer] ──> [Output]

Ducking

[Voice/Narration] ──> [Compressor Sidechain]
[Background Music] ──> [Compressor] ──> [Output]

Music ducks when voice is present.

Compression Cheat Sheet

Tips

1. Don't overcompress: 2-6 dB of gain reduction is usually enough
2. Match levels: Use Makeup Gain to fairly compare compressed vs original
3. Attack is key: It determines if transients punch through
4. Release affects groove: Too fast causes pumping, too slow causes sustained squash
5. Use your ears: Watch meters but trust what sounds good

Related Modules

• VCA - Alternative level control
• EQ - Often used before/after compression
• Distortion - Can add saturation like compressor
• Audio Output - Has built-in limiter

Keyboard Input

Module ID: midi.keyboard Category: MIDI Header Color: Magenta

The Keyboard Input module

Description

The Keyboard Input module converts computer keyboard presses into CV and Gate signals, allowing you to play synthesizer patches without external MIDI hardware. It's the quickest way to test sounds and play melodies.

Inputs

This module has no inputs—it generates signals from keyboard events.

Outputs

Parameters

Keyboard Layout

The computer keyboard is mapped to a piano-style layout:

Lower Row (Z to M) - Lower Octave

| Z | X | C | V | B | N | M |
| C | D | E | F | G | A | B |

| S | D |   | G | H | J |   |
| C#| D#|   | F#| G#| A#|   |

Upper Row (Q to P) - Higher Octave

| Q | W | E | R | T | Y | U | I | O | P |
| C | D | E | F | G | A | B | C | D | E |

| 2 | 3 |   | 5 | 6 | 7 |   | 9 | 0 |   |
| C#| D#|   | F#| G#| A#|   | C#| D#|   |

Octave Controls

• Number keys (or dedicated keys): Change octave
• Octave knob: Set base octave offset

Usage Tips

Basic Synth Playing

Connect to an oscillator for instant playability:

[Keyboard V/Oct] ──> [Oscillator V/Oct]
[Keyboard Gate] ──> [ADSR Gate]

Monophonic vs Polyphonic

The Keyboard module is monophonic—only the most recent key press is active. For polyphonic playing, you'll need multiple keyboard modules or a polyphonic MIDI setup.

Using Glide/Portamento

Set Glide > 0 for smooth pitch transitions:

Glide: 100 ms (subtle slide)
Glide: 300 ms (noticeable portamento)
Glide: 500+ ms (dramatic slide)

The V/Oct output smoothly transitions between notes instead of jumping.

Velocity for Dynamics

Connect Velocity output to create expressive patches:

[Keyboard Velocity] ──> [VCA CV] (louder at higher velocity)
                    ──> [Filter Cutoff CV] (brighter at higher velocity)

Since computer keyboards don't have velocity sensitivity, adjust the Velocity parameter manually or use a MIDI controller.

Octave Switching

Use the Octave parameter to shift the entire keyboard up or down:

• -2: Very low bass notes
• -1: Bass range
• 0: Middle C centered
• +1: Higher register
• +2 to +4: High leads

Playing Techniques

Legato: Hold one key while pressing another—gate stays high, only pitch changes.

Staccato: Quick key presses for short notes.

Trills: Rapidly alternate between two adjacent keys.

Focus and Keyboard Capture

The module receives keyboard input when the application window is focused. Some tips:

• Click on the canvas to ensure focus
• Modifier keys (Ctrl, Alt, Shift) may not be captured
• Some shortcuts may conflict with application functions

Connection Examples

Simple Monosynth

[Keyboard V/Oct] ──> [Oscillator V/Oct]
[Keyboard Gate] ──> [ADSR] ──> [VCA CV]
[Oscillator] ──> [Filter] ──> [VCA] ──> [Output]

Velocity-Sensitive Patch

[Keyboard V/Oct] ──> [Oscillator V/Oct]
[Keyboard Gate] ──> [ADSR Gate]
[Keyboard Velocity] ──> [Attenuverter] ──> [Filter Cutoff CV]
[Keyboard Velocity] ──> [VCA Level CV]

Portamento Lead

[Keyboard V/Oct] ──> [Oscillator V/Oct]
         (Glide: 200ms)

Dual Oscillator Tracking

[Keyboard V/Oct] ──> [Oscillator 1 V/Oct]
                 ──> [Oscillator 2 V/Oct]

Both oscillators track the keyboard pitch.

Keyboard Shortcuts

Comparison with MIDI Note

Use Keyboard for quick testing; use MIDI Note for performance.

Tips

1. Start with Keyboard: Test patches quickly before setting up MIDI
2. Use Glide: Makes simple patches more expressive
3. Mind the focus: Click the window if keys aren't responding
4. Combine with MIDI: Use Keyboard for development, MIDI Note for performance

Related Modules

• MIDI Note - External MIDI input
• Oscillator - Primary V/Oct destination
• ADSR Envelope - Gate destination
• VCA - Velocity destination

MIDI Note

Module ID: midi.note Category: MIDI Header Color: Magenta

The MIDI Note module

Description

The MIDI Note module receives MIDI input from external devices (keyboards, controllers, DAWs) and converts it to CV and Gate signals. It's the bridge between the MIDI world and the modular CV/Gate paradigm.

Inputs

Outputs

Parameters

How It Works

When MIDI data arrives:

1. Note On: Gate goes high, V/Oct updates to pitch, Velocity captures velocity
2. Note Off: Gate goes low (or when all keys released)
3. Aftertouch: Continuous pressure data
4. Mod Wheel (CC1): Updates Mod Wheel output
5. Pitch Bend: Updates Pitch Bend output

V/Oct Conversion

MIDI notes convert to V/Oct standard:

• MIDI note 60 (Middle C) = 0.0V
• MIDI note 72 (C5) = 1.0V (+1 octave)
• MIDI note 48 (C3) = -1.0V (-1 octave)
• Each semitone = 1/12 volt (0.0833...)

Usage Tips

Basic MIDI Connection

Connect to any MIDI device:

[MIDI Note V/Oct] ──> [Oscillator V/Oct]
[MIDI Note Gate] ──> [ADSR Gate]
[MIDI Note Velocity] ──> [VCA CV] (optional)

Velocity-Sensitive Patch

Use velocity for expression:

[MIDI Note Velocity] ──> [Attenuverter] ──> [Filter Cutoff CV]
                     ──> [VCA CV]

Harder playing = louder and brighter.

Pitch Bend

Add pitch bend to oscillator:

[MIDI Note V/Oct] ──────────────────────> [Oscillator V/Oct]
[MIDI Note Pitch Bend] ──> [Attenuverter] ──> [Oscillator FM]

Scale the pitch bend amount with the attenuverter.

Mod Wheel Modulation

Use mod wheel for real-time control:

[MIDI Note Mod Wheel] ──> [LFO Depth] (vibrato amount)
                      ──> [Filter Cutoff CV]
                      ──> [Effect Parameter]

Channel Selection

Omni Mode: Responds to all MIDI channels (default) Specific Channel (1-16): Only responds to that channel

Use specific channels when:

• Multiple MIDI devices are connected
• Splitting keyboard zones
• Receiving from a DAW with multiple tracks

Voice Modes

When multiple keys are pressed (monophonic mode):

Last: Most recently pressed note takes priority Low: Lowest note takes priority High: Highest note takes priority

Aftertouch Expression

If your MIDI controller supports aftertouch:

[MIDI Note Aftertouch] ──> [Filter Cutoff CV]
                       ──> [VCA CV]
                       ──> [Vibrato Depth]

Pressing harder after the initial attack adds modulation.

Velocity Curves

Choose based on your playing style and controller.

MIDI Learn

For parameters that support MIDI Learn:

1. Right-click the parameter knob
2. Select "MIDI Learn"
3. Move the desired MIDI controller
4. The parameter is now mapped

Connection Examples

Complete Velocity-Sensitive Synth

[MIDI Note V/Oct] ──> [Oscillator V/Oct]
[MIDI Note Gate] ──> [ADSR] ──> [VCA CV]
[MIDI Note Velocity] ──> [Filter Cutoff CV]
                     ──> [ADSR Velocity Scale]

With Pitch Bend and Mod Wheel

[MIDI Note V/Oct] ──> [Oscillator 1 V/Oct]
                  ──> [Oscillator 2 V/Oct]
[MIDI Note Pitch Bend] ──> [Mixer] ──> [Oscillator FM]
[MIDI Note Mod Wheel] ──> [LFO] ──> [Mixer]

Multi-Timbral Setup

[MIDI Note (Ch 1)] ──> [Synth Voice 1]
[MIDI Note (Ch 2)] ──> [Synth Voice 2]

Performance Controller

[MIDI Note Mod Wheel] ──> [Filter Cutoff CV]
[MIDI Note Aftertouch] ──> [Vibrato Amount]
[MIDI Note Pitch Bend] ──> [Pitch CV Offset]

Troubleshooting

No MIDI Input

1. Check MIDI device is connected and powered
2. Verify MIDI channel settings match
3. Check that the device is selected in system MIDI settings
4. Try "Omni" channel mode

Wrong Pitch

1. Verify oscillator is calibrated to V/Oct
2. Check for octave offset settings
3. Ensure no unintended pitch modulation

Stuck Notes

1. Check Gate connections
2. Send All Notes Off from your controller
3. Reload the patch

Related Modules

• Keyboard Input - Computer keyboard alternative
• MIDI Monitor - Debug MIDI data
• Oscillator - V/Oct destination
• ADSR Envelope - Gate destination

MIDI Monitor

Module ID: midi.monitor Category: MIDI Header Color: Magenta

The MIDI Monitor module

Description

The MIDI Monitor displays incoming MIDI data in real-time, helping you debug MIDI connections, verify controller mappings, and understand what data your MIDI devices are sending. It's an essential diagnostic tool.

Inputs

Outputs

This module has no outputs—it's purely for monitoring.

Display Elements

The monitor shows real-time MIDI activity:

Note Display

Note: C4 (60) Vel: 100 Ch: 1

Shows note name, MIDI number, velocity, and channel.

CC Display

CC 1: 64  (Mod Wheel)
CC 7: 100 (Volume)

Shows controller number, value, and common CC names.

Pitch Bend

Bend: +0.50

Shows pitch bend position (-1.0 to +1.0).

Aftertouch

AT: 45 (Channel)

Shows aftertouch pressure value.

Activity Indicators

• LED flashes on any MIDI activity
• Separate indicators for Notes, CC, etc.

Parameters

Usage Tips

Debugging MIDI Connections

1. Add a MIDI Monitor to your patch
2. Play your MIDI controller
3. Watch the display for incoming data

If nothing appears:

• Check MIDI cable connections
• Verify MIDI device is selected in system settings
• Try a different MIDI channel

Learning Controller Mappings

Find out what CC numbers your controller sends:

1. Add MIDI Monitor
2. Move a knob/fader on your controller
3. Note the CC number displayed
4. Use that CC number for MIDI Learn

Verifying Velocity Response

Check that velocity is being transmitted:

1. Watch the velocity values while playing
2. Play soft and hard to see range
3. Adjust velocity curve if needed

Checking Pitch Bend Range

Verify pitch bend is working:

1. Move the pitch bend wheel fully
2. Watch the Bend value
3. Should range from -1.0 to +1.0

Troubleshooting Stuck Notes

If notes are stuck:

1. Watch for Note Off messages
2. Check for matching Note On/Off pairs
3. A missing Note Off indicates a MIDI problem

Channel Identification

When using multiple MIDI devices:

1. Set Channel Filter to "All"
2. Play each device
3. Note which channel each uses
4. Configure MIDI Note modules accordingly

Common MIDI CC Numbers

Display Format Examples

Note On

[NOTE] C4 (60) vel:100 ch:1 ON

Note Off

[NOTE] C4 (60) ch:1 OFF

Control Change

[CC] #1 = 64 ch:1 (Mod Wheel)

Pitch Bend

[BEND] +0.245 ch:1

Aftertouch

[AT] pressure:78 ch:1

Connection Examples

Basic Monitoring

[MIDI Device] ──> [MIDI Monitor]
              ──> [MIDI Note] ──> [Synth]

Monitor MIDI while also using it.

Multi-Channel Debugging

[MIDI Device] ──> [MIDI Monitor (All Channels)]
              ──> [MIDI Note (Ch 1)] ──> [Bass Synth]
              ──> [MIDI Note (Ch 2)] ──> [Lead Synth]

Controller Programming

[MIDI Controller] ──> [MIDI Monitor]

Use monitor to learn what your controller sends before mapping.

Tips

1. Always useful during setup: Add a monitor when connecting new MIDI gear
2. Filter noise: Use channel filtering if one device is too active
3. Watch for patterns: MIDI problems often show up as missing events
4. Remove when done: Monitor uses some resources; remove in final patches
5. Check both ends: If nothing appears, verify MIDI is being sent from the source

Troubleshooting Guide

Related Modules

• MIDI Note - Convert monitored MIDI to CV
• Keyboard Input - Alternative non-MIDI input

Oscilloscope

Module ID: util.oscilloscope Category: Visualization Header Color: Cyan

The Oscilloscope module

Description

The Oscilloscope provides real-time visualization of audio and control signals. It displays waveforms, helping you understand what's happening in your patch, debug signal problems, and learn how different modules affect signals.

Inputs

Outputs

Parameters

Display Elements

Waveform Display

The main area shows the signal amplitude over time:

• Horizontal axis: Time (left = past, right = present)
• Vertical axis: Amplitude (-1.0 to +1.0)
• Channel 1: Typically blue trace
• Channel 2: Typically orange trace (overlay)

Grid

Reference grid helps estimate values:

• Horizontal lines at -1, -0.5, 0, +0.5, +1
• Vertical time divisions based on Time setting

Measurements

May display:

• Frequency: Detected fundamental frequency
• Peak-to-Peak: Amplitude range
• DC Offset: Average signal level

Usage Tips

Viewing Oscillator Waveforms

See what your oscillator outputs:

[Oscillator] ──> [Oscilloscope Input 1]
             ──> [Rest of patch]

Verify waveform shape, frequency, and level.

Comparing Two Signals

View two signals overlaid:

[Oscillator 1] ──> [Scope Input 1]
[Oscillator 2] ──> [Scope Input 2]

Useful for:

• Comparing waveforms
• Checking phase relationships
• Viewing before/after processing

Viewing Envelopes

See envelope shape in real-time:

[ADSR Output] ──> [Oscilloscope Input 1]

Adjust Time to 100-500ms to see the full envelope cycle.

Viewing LFO

Check LFO waveform and rate:

[LFO] ──> [Oscilloscope Input 1]

Time setting should be longer than one LFO cycle.

Debugging Signal Problems

No sound? Check the scope:

[Mystery Signal] ──> [Oscilloscope]

• Flat line: No signal
• Clipped/squared-off peaks: Distortion/clipping
• DC offset: Signal not centered around zero
• Expected waveform: Signal is fine, problem is elsewhere

Stable Display with External Trigger

For synced display of periodic signals:

[Clock] ──> [Oscilloscope Trigger]
[Signal] ──> [Oscilloscope Input]

The display starts at the same point each cycle.

Trigger Modes

Auto: Triggers automatically if no trigger detected Normal: Only displays when trigger threshold is crossed Single: Captures one sweep, then freezes (for transients)

Using Thru Outputs

The scope passes signals through, so it can be inserted anywhere:

[Osc] ──> [Scope Input 1]
[Scope Thru 1] ──> [Filter] ──> [Scope Input 2]
[Scope Thru 2] ──> [VCA] ──> [Output]

See signal before and after filter.

Setting Time Scale

Amplitude Scaling

If signal is too quiet or too loud:

• Use Scale knob to zoom in/out
• 1x = full range display
• 2x = shows half range (zoomed in)
• 0.5x = shows double range (zoomed out)

What to Look For

Healthy Signals

Problem Signs

Connection Examples

Signal Chain Analysis

[Osc] ──> [Scope In 1, Thru 1] ──> [Filter] ──> [Scope In 2, Thru 2] ──> [Output]

Envelope Visualization

[Gate] ──> [ADSR] ──> [Scope In 1]

LFO Phase Check

[LFO 1] ──> [Scope In 1]
[LFO 2] ──> [Scope In 2]

Pre/Post Effect

[Audio] ──> [Scope In 1, Thru 1] ──> [Distortion] ──> [Scope In 2]

Tips

1. Insert anywhere: Use Thru outputs to monitor without breaking the signal chain
2. Match time to signal: Audio needs fast time, envelopes need slow time
3. Use trigger: For stable display of periodic signals
4. Two channels: Compare before/after or two related signals
5. Check levels: Scope shows you clipping before you hear it

Related Modules

• Oscillator - Waveforms to visualize
• LFO - Modulation to visualize
• ADSR Envelope - Envelopes to visualize
• MIDI Monitor - MIDI visualization alternative

Audio Output

Module ID: output.audio Category: Output Header Color: Red

The Audio Output module

Description

The Audio Output module is the final destination for your audio signal, sending sound to your computer's audio interface. It provides master level control, metering, and a built-in limiter to prevent clipping.

Every patch that makes sound needs exactly one Audio Output module.

Inputs

Outputs

This module has no outputs—it sends audio to the system.

Parameters

Display Elements

Level Meters

Stereo LED-style meters showing:

• Green: Safe levels (-∞ to -6 dB)
• Yellow: Moderate levels (-6 to -3 dB)
• Red: Hot levels (-3 to 0 dB)
• Clip indicator: Flashes on limiting/clipping

Limiter Activity

LED indicates when limiter is actively reducing gain.

How It Works

1. Mixing: Left, Right, and Mono inputs are summed appropriately
2. Level: Master level is applied
3. Limiter: If enabled, prevents signal from exceeding threshold
4. Output: Signal is sent to the audio hardware

Input Routing

• Left only: Duplicated to both outputs (mono)
• Right only: Duplicated to both outputs (mono)
• Mono only: Sent to both outputs
• Left + Right: True stereo
• All three: Mono added to stereo

Usage Tips

Basic Connection

Simplest setup—one source to mono:

[VCA] ──> [Output Mono]

Sound comes from both speakers equally.

Stereo Connection

True stereo from stereo effects:

[Delay Left] ──> [Output Left]
[Delay Right] ──> [Output Right]

Mono + Stereo

Add a mono source to a stereo mix:

[Bass VCA] ──> [Output Mono]
[Pad Left] ──> [Output Left]
[Pad Right] ──> [Output Right]

The bass appears center, pad is stereo.

Proper Gain Staging

For best sound quality:

1. Keep individual module outputs at reasonable levels
2. Use VCAs and mixers to control levels
3. Set Output Level near 0 dB
4. Watch for limiter activation—occasional is fine, constant indicates too hot

Limiter Usage

The built-in limiter prevents harsh digital clipping:

Limiter On (recommended):

• Peaks are caught and reduced
• Protects your ears and speakers
• Slight compression on peaks

Limiter Off:

• True clipping on overs
• Harsh digital distortion
• May be desired for effect

Monitoring Levels

Watch the meters while working:

Avoiding Clipping

If limiter is constantly engaged:

1. Lower Level knob on Output module
2. Lower levels earlier in the signal chain
3. Use VCAs to control dynamics
4. Consider a compressor before output

Testing Patches

When building patches:

1. Start with Output Level low
2. Gradually increase while playing
3. Find a comfortable level
4. Leave headroom for dynamics

Multiple Sound Sources

When mixing multiple voices:

[Voice 1] ──> [Mixer Ch 1]
[Voice 2] ──> [Mixer Ch 2]
[Mixer] ──> [Output Mono]

Use a mixer before output rather than connecting multiple sources.

Connection Examples

Simple Mono Synth

[Oscillator] ──> [Filter] ──> [VCA] ──> [Output Mono]

Stereo Synth with Effects

[Synth] ──> [Reverb L] ──> [Output Left]
            [Reverb R] ──> [Output Right]

Full Mix

[Bass] ──> [Mixer Ch 1]
[Lead] ──> [Mixer Ch 2]
[Pad L/R] ──> [Mixer Ch 3/4]
[Mixer L] ──> [Output Left]
[Mixer R] ──> [Output Right]

Troubleshooting

No Sound

1. Check that Output module exists in patch
2. Verify inputs are connected
3. Check Level knob isn't at minimum
4. Verify system audio output settings
5. Check speakers/headphones are connected
6. Use Oscilloscope to verify signal is reaching Output

Distorted Sound

1. Lower Level knob
2. Watch for constant limiter activation
3. Reduce levels earlier in chain
4. Check for feedback loops in patch

One Channel Only

1. Check if only Left or Right is connected
2. Verify stereo effect settings
3. Use Mono input for mono sources

Audio Glitches/Dropouts

1. Reduce patch complexity
2. Build with release mode (cargo run --release)
3. Close other audio applications
4. Check audio buffer settings

Technical Notes

Sample Rate

Operates at system audio sample rate (typically 44.1 kHz or 48 kHz).

Bit Depth

Internal processing at 32-bit float, converted to system format on output.

Latency

Minimal latency determined by audio buffer size. Lower buffer = lower latency but higher CPU.

Tips

1. One output module per patch: Multiple outputs will conflict
2. Use the limiter: It's there to protect you
3. Watch your levels: Meters are there for a reason
4. Gain stage properly: Don't rely on the limiter for level control
5. Start quiet: You can always turn up, but can't unhear loud surprises

Related Modules

• VCA - Level control before output
• Mixer - Combine signals before output
• Compressor - Dynamics control before output
• Oscilloscope - Visualize what you're sending

Basic Subtractive Synth

A classic subtractive synthesizer with oscillators, filter, envelope, and modulation.

The basic subtractive synth patch

Overview

Subtractive synthesis starts with a harmonically rich waveform (saw or square) and uses a filter to "subtract" frequencies, shaping the tone. Combined with envelopes for dynamic control, this creates expressive, versatile sounds.

Character: Warm, punchy, expressive Good for: Bass, leads, pads, keys

Modules Used

• 1x Oscillator
• 1x SVF Filter
• 1x VCA
• 2x ADSR Envelope
• 1x Keyboard Input
• 1x Audio Output

Patch Diagram

┌──────────┐      ┌──────────┐      ┌─────┐      ┌────────┐
│ Keyboard │─V/Oct─▶│Oscillator│─Audio─▶│Filter│─Audio─▶│  VCA   │─▶ Output
│          │      │  (Saw)   │      │(SVF) │      │        │
└────┬─────┘      └──────────┘      └───▲──┘      └───▲────┘
     │                                  │             │
     │ Gate                             │             │
     │         ┌──────────┐             │      ┌──────┴──────┐
     └────────▶│  ADSR 1  │─────────────┘      │   ADSR 2    │
               │ (Filter) │                    │ (Amplitude) │
               └──────────┘                    └─────────────┘
                                                      ▲
                                                      │ Gate
               ┌──────────────────────────────────────┘
               │
        [From Keyboard Gate]

Step-by-Step Setup

1. Add Core Modules

Add and position:

1. Keyboard Input (left side)
2. Oscillator (center-left)
3. SVF Filter (center)
4. VCA (center-right)
5. Audio Output (right)

2. Create the Audio Path

Connect the main audio signal:

[Oscillator Audio Out] ──▶ [Filter Input]
[Filter Lowpass Out] ──▶ [VCA Input]
[VCA Output] ──▶ [Audio Output Mono]

3. Add Pitch Control

[Keyboard V/Oct] ──▶ [Oscillator V/Oct]

4. Add Amplitude Envelope

Add ADSR 1 for volume control:

[Keyboard Gate] ──▶ [ADSR 1 Gate]
[ADSR 1 Env] ──▶ [VCA CV]

ADSR 1 Settings (Amplitude):

5. Add Filter Envelope

Add ADSR 2 for filter movement:

[Keyboard Gate] ──▶ [ADSR 2 Gate]
[ADSR 2 Env] ──▶ [Filter Cutoff CV]

ADSR 2 Settings (Filter):