Sustain

On a synthesizer, sustain describes the period of time after the attack and decay phases of the amplitude envelope during which a sound is maintained at a constant volume. It regulates the amplitude envelope of the sound and is typically found in the envelope section of a synthesizer. The four stages of the amplitude envelope—a graph that depicts how a sound’s volume changes over time—are attack, decay, sustain, and release.

The sustain stage, which comes after the decay stage and is the third stage of the amplitude envelope, determines how long the sound will be held at a constant volume following the attack and decay stages. A sound will be held for a longer time when the sustain value is higher, while a sound will be held for a shorter time when the sustain value is lower.

The sustain parameter can produce various effects and is especially helpful for modifying the sound of percussive instruments like drums, pianos, and plucked instruments. It is possible to create a sound that lingers by using a high sustain value and a more transient sound by using a low sustain value.