A MIDI-CV interface converts MIDI notes into the pitch voltage and gate a modular understands

Oscillators and envelopes in a modular respond to voltage, not MIDI, so a MIDI-CV interface translates incoming MIDI notes into control voltages. Its two core outputs are pitch CV (the note number as a 1 V/octave signal) and a gate (high, e.g. 10 V, while the key is held; 0 V when released). This split is fundamental: the pitch line sets an oscillator’s frequency while the gate line triggers an envelope, so one played note simultaneously chooses a pitch and opens a voice. Interfaces typically also expose velocity CV, aftertouch, pitch- and mod-wheel CV, and MIDI clock plus start/stop for sync. Some (e.g. the Doepfer A-190-1) broadcast CV and gate onto the system’s internal bus so bus-connected modules receive pitch and gate automatically. Because voltage-controlled modules (VC-ADSR, VC-LFO) can then be driven by MIDI continuous controllers, and those CCs can be recorded by a sequencer, otherwise un-storable modular parameters become effectively programmable.

Examples

Patch MIDI-CV V/OCT into a VCO’s V/OCT and MIDI-CV GATE into an ADSR’s gate input, then the ADSR into a VCA: pressing a key sets the pitch and opens the amplitude envelope for as long as the key is held. Route a mod-wheel CC to the interface’s second CV output → VCF cutoff, and record it into a DAW to automate a filter sweep on an analog voice.

Assessment

Trace the signal flow from a MIDI keyboard through a MIDI-CV interface to a VCO→VCF→VCA voice, labelling each link as pitch CV, gate, or audio. Explain which output sets the oscillator’s pitch and which tells the envelope when the note starts and ends, and why both are needed to sound one played note.