Envelope

The shape of a sound's level over time, described by how quickly it arrives, how it settles, how long it holds and how it dies away.

Every note has one, whether or not anything is processing it. On guitar the shape is set by how the string is picked, where along its length it is played, how much of the body or bridge is involved, and how much the instrument sustains. Effects that respond to the envelope, such as filters, gates and compressors, are really following this same curve, which is why they react differently to a stab and a slow arpeggio.

Example: the same chord struck with a hard pick has a much sharper envelope than one rolled with the thumb, and a compressor set with a slow attack will let that difference through.

Envelope

See also