A hardware device or software routine that generates a sound envelope. Also known as a contour generator or transient generator because the envelope is a contour (shape) that is used to create some of the transient (changing) characteristics of the sound over time. The purpose of an envelope generator is to give a shape to each note. By itself, an envelope generator makes no sound. Its output is used as a control source that tells some other part of the synthesizer what to do. Typical synths have three envelope generators for each oscillator: one to control pitch, one to control the filter rolloff, and one to control amplitude. See ADSR