Envelopes: shaping a note in time
ADSR, the four-stage loudness contour — with the typical times that make plucks, keys, and pads.
Hold the lesson-1 oscillator’s play button and it sits at full level until you stop it. Real instruments never behave this way. A piano note is loudest in its first instant and then fades for seconds; a bowed string swells in and holds. The loudness contour across a note’s lifetime matters so much to recognition that classic psychoacoustics experiments found familiar instruments hard to identify with just the first tens of milliseconds cut off the recording. Synthesizers draw this contour with an envelope: a curve that runs once per note, triggered when the note starts. The four-stage ADSR layout has been the standard since the 1970s because four numbers cover most musical needs.
The ADSR contour. Attack, decay, and release are times; sustain is a level (the dashed line). Note-on starts the curve; note-off starts the release from wherever the curve happens to be at that moment.
The four stages, with numbers
- Attack — the time from silence to peak, starting at note-on. Below about 5 ms the note begins with a hard, clicky edge (drums, plucks); 20–80 ms gives a soft push (keys, organs); above 200 ms the note audibly swells in (strings, pads).
- Decay — the time to fall from the peak to the sustain level. With sustain set low, decay effectively decides how long the note’s front lasts; 100–300 ms is the classic zone for plucks and keys.
- Sustain — the level held for as long as the note stays down. It is the only stage measured as a level, not a time, and the source of most beginner confusion: with sustain at 100% the decay stage does nothing audible, and with sustain at 0% every note dies out even while held.
- Release — the time to fade from the current level to silence after note-off. Short releases (under ~100 ms) sound dry and tight; long ones (1 s and up) leave tails that overlap the following notes, which is a large part of how pads blur together.
Pluck and pad, the two archetypes
Two settings cover a surprising share of real patches. A pluck — near-instant attack, quick decay, zero sustain, short release — is the energy profile of everything struck or plucked in the physical world. A pad — slow attack, high sustain, long release — has no transient at all, only swell and wash. Between the two sit keys (fast attack, medium decay, moderate sustain) and brass (medium attack, high sustain). When a patch sounds wrong in a track, check its envelope before touching the timbre; the loudness contour usually matters more than the tone.
Both archetypes on one time axis: the pluck spends its energy immediately; the pad takes longer to arrive than the pluck takes to finish.
Hold the button and let go at different moments. With sustain up, the note waits for you; with sustain at zero, it ends on its own schedule no matter how long you hold. Drag attack long and the note grows a slow front. Load each preset, then rebuild it by hand once — numbers learned through fingers stay learned.
Every device carries the amplitude envelope on its AMP page, stages printed on the knobs. Elektron adds a fifth stage, HOLD, between attack and decay: a fixed time at peak level before the decay starts, which gives drum hits a solid body before the tail.