ZynAddSubFX/ADSR Envelope

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How the four parameters change the shape of an envelope.

The ADSR envelope is the basic tool to create synthetic sounds. The ADSR acronym means: Attack, Decay, Sustain and Release.

  • Attack is how the sound starts from silence (time and strength);
  • Decay is the way the sound changes after the attack to the main sound (sustain);
  • Sustain is the main sequence of the sound;
  • Release is how the sound stops.

Taking the example of an electronic keyboard, attack followed by decay are heard when pressing a key, sustain is the actual note while the key is down, and release happens when freeing the key.


Simple envelope[edit]

ADSR simple envelope example

This is a basic sound with very short attack and quick release:


ADSR envelope with a 500ms attack

The attack goes linearly from silence to the maximal sound in 500 ms:


ADSR envelope with a decay

A decay halves the volume down after the attack:


ADSR envelope without sustain

There's no sustain in this one, the sound stops immediately even without releasing the key:


ADSR envelope with 1 second release

The release lasts 1 second from sustain level to silence:

Envelope types and controls[edit]

Amplitude envelope controls
Frequency envelope controls
Filter envelope controls
Bandwidth envelope controls

There are four different envelopes in ZynAddSubFX and each has its own set of options and controls.

The ADSR controls are found -at least partly- in all of them, as:

  • A.DT: attack duration
  • A.VAL: attack value
  • D.DT: decay duration
  • D.VAL: decay value
  • S.VAL: sustain value
  • R.DT: release duration
  • R.VAL: release value

Toggle buttons include:

  • FRCR: forced release, means that if this option is turned on, the release will go to the final value, even if the sustain stage is not reached. Usually, this must be set.
  • LIN/LOG: linear or logarithmic, toggles between linear and logarithmic interpolation (default is linear).

The stretch value: how the envelope is stretched according to the note. On the higher notes the envelopes are shorter than lower notes. The stretch range is from 0 (leftmost) to 200% (rightmost). 200% means that the envelope is stretched about 4 times/octave.