The multiplier: output = signal x control x Gain. The left inlet is the signal, the right inlet the control; an unconnected control reads as unity, so a bare VCA is just a gain.
This is the glue that makes control signals do something:
LFO -> control inlet: tremolo.
Follower -> control inlet: gate/expander (or ducking, inverted via a Number chain).
Audio -> control inlet with Bipolar on: ring modulation.
Without Bipolar the control is clamped at zero so ordinary unipolar control signals can't flip the signal's phase; Bipolar passes negatives through for audio-rate modulation.
Parameters
| Gain | a fixed multiplier on top of the control inlet. With nothing patched there this is the whole story, and the VCA is simply a gain. |
| Bipolar | lets the control go negative, which is what makes audio-rate modulation possible. Off it is clamped at zero, so a unipolar control can never flip the phase of what passes through. |