Operator

There are a few different synthesis techniques where one usually audio-rate signal does something to another audio signal. For example, in frequency modulation (FM), a second signal (called the modulator) varies the frequency (pitch) of the main signal, called the carrier. These two signals or oscillators are often referred to as operators, particularly in FM patches. You’re more likely to hear this term used when working with a dedicated FM synthesizer like a Yamaha DX-7 and its descendants, than with a modular system.