EnvelopeA simple ADSR (Attack, Decay, Sustain, Release) envelope that's triggered every time a note is pressed. Traditionally used to control the volume of notes or the cutoff frequencies of filters.
To keep the language simple, these explanations assume you're controlling the volume of an oscillator.
Attack: The amount of time it takes for the controlled signal to reach it's peak volume.
Decay: The amount of time it takes to reach the sustain volume after the attack is complete.
Sustain: The volume the the oscillator will play at until the note is released.
Release: The amount of time it takes after the note is released for the signal to fade to silence.