Amplitude ADSR

▸What it is

The amplitude envelope is the volume contour of a note from press to release. Four stages: Attack (how long to reach full volume after a key is pressed), Decay (how long to fall from peak to the sustained level), Sustain (the held volume while the key is still pressed), Release (how long the sound fades after the key is let go). Fast attack and decay with low sustain make percussive plucks. Slow attack with high sustain makes pads that swell in. The amp envelope does not change tone; it only shapes loudness over time. Almost everything that sounds expressive is doing something interesting with this contour — whether you can hear the envelope explicitly or not.

▸Questions

• What is the difference between decay and release?

  Decay runs while you are still holding the key, dropping from peak down to the sustain level. Release runs after you let go, fading from wherever the volume currently is down to silence.

• Why does a long attack make my bass feel late?

  Because the note is literally inaudible during the attack. For tight, on-beat bass, attack should be near zero.

• Sustain is a level, not a time — is that right?

  Yes. Attack, decay, and release are durations. Sustain is the level the envelope holds at while a key is down.

▸In the curriculum

First taught

BS2 · Shape the note — Dial punch vs sustain on the amplitude ADSR. Part of the Bass track.

Reused in

The same concept comes back in 3 lessons later in the curriculum, in a new context.

▸Related concepts

Concepts that share a lesson with amplitude adsr: