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

Type	Color	Range	Primary Use
Audio	Blue	-1.0 to 1.0	Sound signals
Control	Orange	0.0 to 1.0 (unipolar) or -1.0 to 1.0 (bipolar)	Modulation, CV
Gate	Green	0.0 or 1.0	Triggers, on/off states
MIDI	Purple	Structured data	Note/CC messages

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.