A VCA sets signal level in proportion to a control voltage, acting as a voltage-operated volume knob

A Voltage-Controlled Amplifier (VCA) varies the amplitude of a signal passing through it in proportion to an incoming control voltage (CV). Near 0 V CV the output is typically silent; as CV rises, more signal passes; at maximum CV the signal passes at full level. In a standard voice the VCA sits at the end of the signal path, driven by an envelope generator patched to its CV input: the envelope’s voltage shapes loudness over time (attack, decay, sustain, release), so a note has a defined start, body, and tail. Without a VCA an oscillator runs continuously — a bare oscillator patched to the output is always a drone. VCAs also process CV, not just audio, enabling voltage-controlled modulation depth: routing an LFO through a VCA sets how much vibrato or tremolo is applied.

Examples

Oscillator → VCA signal in; ADSR → VCA CV in; sequencer gate → ADSR gate. Each step fires the envelope, shaping the oscillator into a note. Non-audio use: LFO → VCA → pitch input gives voltage-controlled vibrato depth.

Assessment

Explain why an oscillator patched straight to the output sounds like a continuous drone, then give the minimal patch to make a note with a clear attack and release. Name one non-audio use of a VCA in a patch.