Envelope generator [envelope shaper]
- Anne Beetem Acker
Electronic circuit that controls a voltage-controlled amplifier (VCA), voltage-controlled filter (VCF), or voltage-controlled oscillator (VCO), allowing the output behaviour (or envelope, as the output curve is known in electronics) of a sound signal to be shaped over time. When controlling a VCA the envelope generator shapes volume; controlling a VCF affects timbre, while mixing signals to a VCA and VCO produces a frequency contour. The most common envelope shaper, the ADSR (Attack, Decay, Sustain, Release), generates a four-segment signal that allows for setting the rise and fall rates for the attack, decay, and release, and setting a level for the sustain. Some ADSRs allow each segment to be scaled proportionately to an input signal such as key velocity. Advanced envelope generators, such as a UEG (universal event generator), can have hundreds of segments for which time and slope can be set, and provide a means to repeat, skip, or abbreviate a segment....