The voltage-controlled oscillator (VCO) is a typical analog audio oscillator with 1V/Oct pitch tracking for musical purposes. VCOs are one of the most basic audio sources in a synthesizer. Their sound is usually further shaped and refined by filters, wavefolders, voltage-controlled amplifiers (VCAs) and other audio effects.

https://wiki.aemodular.com/pmwiki.php/AeManual/VCO