The ADSR Envelope

Four stages shape the attack, the sustain and the tail of every note.

Related

TimbreVelocityOrganModern

The question

With the same oscillator and filter, why does one patch read as a pluck and another as a pad? Often it is not the waveform but the four envelope stages.

How it works

Attack rises to peak, decay falls to sustain, sustain holds while the key is down, and release returns to zero when it lifts. Attack and decay are times, sustain is a level. It can also shape cutoff, pitch or pulse width. Velocity often maps to envelope amount, so a harder note opens brighter. Exponential shapes usually sound more natural than straight lines.

Settings and what you hear

An attack of a few milliseconds reads as a pluck or a hit; tens to hundreds of milliseconds read as a bow or breath. A short decay separates the attack, a long one joins it to sustain. High sustain reads as an organ, low as a pluck. A long release overlaps notes, a short one closes cleanly.

What to listen for

Hear the saw lead and the long pad, noting the fast attack and short release of the first against the slow ends of the second. Then hear the tubular bells and the organ; one decays after a strike, the other sounds while held. Finally compare nylon and muted guitar, same attack, different decay length.

Common misconceptions

That sustain is a length of time, when it is a level; that release is reverb, when it belongs to the note itself; that a shorter attack is always clearer, when too short clicks.

Sources

• Gordon Reid, Sound On Sound Synth Secrets — envelope stages checked, not quoted
• Curtis Roads, The Computer Music Tutorial — amplitude envelopes checked, not quoted

Used for fact-checking only; all prose is original.