Equipment

Synthesizers : frequency modulation (FM) synthesis

John Chowning of Stanford University is generally considered to be the first researcher to conceive of producing musical sounds by causing one oscillator to modulate the pitch of another. This is called FM, or frequency modulation, synthesis. Chowning's early FM experiments were done with software on a mainframe computer.

Sine wave oscillators

FM uses sine-wave oscillators (called operators) which, in order for their fundamental frequency to be sufficiently stable, are normally generated digitally. Each operator's audio output may be fed to the input of another operator, via an ADSR or other envelope controller. The first operator modulates the pitch of the second operator, in ways that can produce complex waveforms. FM synthesis is fundamentally a type of additive synthesis and the filters used in subtractive synthesizers were typically not used in FM synthesizers until the mid-1990s. By cascading operators and programming their envelopes appropriately, some subtractive synthesis effects can be simulated, though the sound of a resonant analog filter is almost impossible to achieve. FM is well-suited for making sounds that subtractive synthesizers have difficulty producing, particularly non-harmonic sounds, such as bell timbres.

Yamaha & Stanford

Chowning's patent covering FM sound synthesis was licensed to giant Japanese manufacturer Yamaha, and made millions for Stanford during the 1980s. Yamaha's first FM synthesizers, the GS-1 and GS-2, were costly and heavy. They soon followed the GS series with a pair of smaller, preset versions - the CE20 and CE25 Combo Ensembles [1]- which were targeted primarily at the home organ market and featured four-octave keyboards. Their third version, the DX-7 (1983), was about the same size and weight as the Prophet-5, was reasonably priced, and depended on custom digital integrated circuits to produce FM tonalities. The DX-7 was a smash hit and may be heard on thousands of pop recordings from the 1980s. Yamaha later licensed its FM technology to other manufacturers. By the time the Stanford patent ran out, almost every personal computer in the world contained an audio input-output system with a built-in 4-operator FM digital synthesizer -- a fact most PC users are not aware of.

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