Envelope (music)

For example, a piano key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero.

Envelope generators, which allow users to control the different stages of a sound, are common features of synthesizers, samplers, and other electronic musical instruments.

Moog wired a doorbell button to the synthesizer and used a capacitor to store and slowly release voltage produced from hitting a key.

He refined the design to remove the need to push a separate button with every keypress, with two switches on every key: one to produce the control voltage determining pitch and the other to trigger the envelope generator.

Some software synthesizers, such as Image-Line's 3xOSC (included with their DAW FL Studio) have DAHDSR (delay, attack, hold, decay, sustain, release) envelopes.