The SW902 Voltage-Controlled Amplifier is used in any circumstances where variable gain is desired for gating or modulating AC or DC voltage sources. Articulation of a tone or sound, utilizing oscillators, controllers, envelope generators and the VCA is the basic traditional patch around which most performance oriented synthesizers are based. In addition to DC control voltage, the VCA can be controlled by varying voltages (AC) from sources like the SW 901 Oscillator. Slowly varying control voltages (2-9 Hz) can create tremolo or echo like effects upon an audio signal. Audio control frequencies create sidebands with often clangorous effects, usefull for a variety of audio timbres and percussive sounds. The inverting outputs of the VCA can be useful for spatial modulation, signal inverting of control voltages, controlling two oscillators in contrary motion with a single control signal and various amplitude sampling arrangements.