An operator is a fundamental building block that generates or modifies audio signals. An operator typically consists of an oscillator, an envelope generator, and sometimes an amplifier, all working together to create a single audio or modulation signal.
Operators can function as either carriers or modulators:
- Carrier: A carrier operator is the primary audio signal that you hear in an FM synthesis patch. Its frequency and amplitude are modulated by one or more modulator operators, resulting in the final output sound.
- Modulator: A modulator operator is used to modulate the frequency of a carrier operator. It influences the carrier’s frequency according to its own frequency, amplitude, and shape of its envelope. The modulator operator itself is usually not directly audible.
In FM synthesis, operators are interconnected in various configurations called algorithms. These algorithms define how operators are combined, and how they modulate each other. The resulting sound depends on the frequency ratio between the carrier and modulator operators, their envelopes, and the overall algorithm used.
FM synthesis is well-known for its ability to generate a wide range of sounds, from simple sine waves to complex and evolving timbres, by varying the interconnections and parameters of operators.