An ADSR envelope shapes amplitude or timbre over four stages: Attack, Decay, Sustain, Release

An ADSR envelope generator outputs a voltage contour with four segments triggered by a gate signal. Attack: the time the voltage takes to rise from zero to peak when gate goes high. Decay: the time it falls from peak to the sustain level. Sustain: the fixed voltage maintained while gate remains high. Release: the time it falls back to zero after the gate goes low. ADSR envelopes are the primary tool for shaping how sounds evolve over time — fast attack for percussive sounds, long release for pads. The envelope output is typically routed to a VCA (amplitude shaping) and/or a VCF (filter sweep). Attack and release together determine the “bow” and “pluck” feel of a note.

Examples

Drum: very short attack (0 ms), short decay (50 ms), sustain at 0, no release needed — punchy, percussive. Pad: slow attack (500 ms), medium decay, high sustain, long release (2 s) — slow fade in and out.

Assessment

Draw the voltage shape of an ADSR envelope for a note held for 1 second and then released. Describe how changing only the release time affects the perceived character of a bass patch.