Voltage controls oscillator pitch: higher voltage produces higher pitch

In modular synthesis, pitch is controlled by voltage: the voltage-controlled oscillator (VCO) translates an incoming control voltage (CV) into a frequency. The standard is 1V/octave — each additional volt doubles the frequency. When a lower note is played, a lower voltage is sent to the oscillator; when a higher note is played, a higher voltage is sent. This principle is what allows keyboards, sequencers, and other modules to control pitch: they output voltages, not digital MIDI note numbers (or they convert MIDI to CV). The visual corollary is that an oscilloscope or display showing the CV trace moves up and down in sync with the pitch.

Examples

On a modular oscilloscope display, the blue CV line drops when a lower note is played and rises for a higher note. In VCV Rack, patch a VCO’s V/OCT input from a keyboard module; observe the CV meter rise and fall as you play.

Assessment

If a VCO receives 2V and plays A4 (440 Hz), what voltage produces A5 (880 Hz)? Explain the 1V/octave standard and why it is useful for modular integration.