A VCV Rack cable can carry up to 16 voices; a mono modulation source fans out to all voices

VCV Rack supports polyphony: a single cable can carry many independent voices — up to 16, the maximum Rack allows. The number of active voices in a polyphonic module is set by its primary input (for example the 1V/oct input of a VCO, or the gate input of an envelope), so plugging a 4-voice pitch cable into a VCO makes it a 4-voice oscillator. Secondary inputs then follow simple routing: a monophonic (single-voice) modulation source is copied to every voice, so one LFO or one cutoff CV correctly affects all voices at once; a polyphonic source with as many channels as there are voices feeds each voice its own value; and a source with too few channels leaves the extra voices with 0 V (no modulation). Knowing this explains why a mono LFO modulates a whole polyphonic patch, while a partly-polyphonic source can leave some voices unmodulated.

Examples

A 4-voice V/oct cable drives a VCO as 4 voices. A mono LFO into that VCO’s FM input wobbles all 4 voices equally. A 2-voice LFO into an 8-voice patch modulates only voices 1–2; voices 3–8 get 0 V.

Assessment

A polyphonic VCO has an 8-voice pitch input. You patch a 3-voice LFO into its FM input. Which voices receive modulation and which receive 0 V? What would you change so all eight voices are modulated equally?