A VCO, or Voltage Controlled Oscillator, is a fundamental module in modular synthesis. It is an oscillator whose frequency, or pitch, can be adjusted by an external control voltage (CV) input. VCOs generate periodic waveforms, such as sine, triangle, sawtooth, or square waves, which serve as the basis for creating sounds in a modular synthesizer.
VCOs are used to generate raw audio signals that can be further processed by other modules, such as filters, VCAs, and effects units, to create a wide range of sounds and timbres. By adjusting the frequency of a VCO using control voltage inputs, you can create dynamic, expressive, and evolving sounds that respond to changes in voltage from sequencers, keyboard controllers, or other modulation sources.
VCOs can also be used for more advanced synthesis techniques, such as frequency modulation (FM) synthesis or phase modulation (PM) synthesis, by using one VCO to modulate the frequency of another VCO, resulting in complex and harmonically rich sounds.
VCOs can be found in both analog and digital formats, each with their own characteristics and benefits. Analog VCOs are known for their warm, organic sound, while digital VCOs offer precise control and extended functionality.