A circuit which generates a signal, usually meant to control a voltage controlled amplifier for the purpose of giving dynamic contour to a played note (in order words, providing a rise and fall of the volume of the note). Envelope generators have come in many forms over the years, but the simplest and the perennial favorite is the ADSR envelope generator. ADSR is an acronym for «Attack, Decay, Sustain, Release», the four segments of the ADSR generator's output.
Modified version of Yves Usson's Yusynth ADSR envelope generator by Caspar Ockeloen-Korppi
Генератор огибающей на дискретных компонентах
Moog System 55 ADSR Envelope Generator