Sustain is the property of a sound continuing to ring after it is played, or the act of holding a note.
How to use it
Long chords and melodies create space and continuity. On piano this involves the damper pedal, and on a synth it involves the settings.
How it differs from related terms
Sustain is about holding a sound, while legato is about connecting notes smoothly.
Use it in contrast with places that rest, so that the sounds do not pile up too much.
