Envelope

An envelope is a modulation source that outputs a changing value over time rather than a repeating waveform like an LFO. When you press a key, the envelope runs through its stages and drives whatever parameter it is assigned to. The most common shape is the ADSR — attack, decay, sustain, release — but many synths offer multi-stage or freely drawn envelopes with any number of breakpoints. Envelopes are what give a sound its sense of motion and articulation: routed to amplitude they define the volume contour, routed to filter cutoff they create sweeps, and routed to pitch they add clicks or bends. Learning to hear and shape envelopes is fundamental to designing expressive, natural-feeling sounds.