Once it has reached the sustain level, it remains there until the key is released. Once the key is released, the voltage falls back to zero. The time it takes to do this is called the release time. Thus, the user can specify the attack time, the decay time, the sustain level, and the release time. By clever manipulation of the other three parameters, you can invoke simple but convincingly natural changes in a sound, particularly if you have several EGs to work with.
Digital technology makes it possible to produce much more flexible EGs at a much lower cost.
S ome digital synthesizers offer four or more envelope levels, with adjustable rates between each. In all cases, the job of the EG is to produce an aperiodic change in loudness, pitch, timbre, or all of the above.