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
| Port | Signal Type | Description |
|---|---|---|
| Gate | Gate (Green) | Trigger input. Rising edge starts Attack, falling edge starts Release |
| Retrig | Gate (Green) | Retrigger input. Rising edge restarts Attack without waiting for Release |
Outputs
| Port | Signal Type | Description |
|---|---|---|
| Env | Control (Orange) | Main envelope output (0.0 to 1.0) |
| Inv | Control (Orange) | Inverted envelope output (1.0 to 0.0) |
| EOC | Gate (Green) | End of Cycle - outputs pulse when envelope completes Release |
Parameters
| Knob | Range | Default | Description |
|---|---|---|---|
| Attack | 0.1 ms - 10 s | 10 ms | Time to rise from 0 to peak |
| Decay | 0.1 ms - 10 s | 100 ms | Time to fall from peak to Sustain level |
| Sustain | 0.0 - 1.0 | 0.7 | Level held while gate is high |
| Release | 0.1 ms - 10 s | 200 ms | Time to fall from Sustain to 0 after gate low |
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)
| Attack | Decay | Sustain | Release |
|---|---|---|---|
| 1 ms | 200 ms | 0.0 | 100 ms |
Fast attack, immediate decay to silence, short release.
Pad (Strings, Ambient)
| Attack | Decay | Sustain | Release |
|---|---|---|---|
| 500 ms | 1 s | 0.7 | 2 s |
Slow attack, gradual decay, sustained level, long release.
Organ (Sustained)
| Attack | Decay | Sustain | Release |
|---|---|---|---|
| 1 ms | 10 ms | 1.0 | 50 ms |
Instant attack, no decay, full sustain, quick release.
Brass (Soft Attack)
| Attack | Decay | Sustain | Release |
|---|---|---|---|
| 100 ms | 300 ms | 0.8 | 200 ms |
Moderate attack (breath), slight decay, high sustain.
Percussion (Drum, Pluck)
| Attack | Decay | Sustain | Release |
|---|---|---|---|
| 0.1 ms | 100 ms | 0.0 | 50 ms |
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