FM synthesis
Sound synthesis method in which one oscillator modulates the frequency of another.
What it means
FM synthesis, short for frequency modulation synthesis, is a method of electronic sound generation. One oscillator, the carrier, produces a tone whose frequency is rapidly altered by a second oscillator, the modulator. Additional overtones arise as a result, and even with a few oscillators complex, often metallic or bell-like tones can be produced.
Musical use
The method was discovered in the late 1960s by John Chowning at Stanford University and published in 1973. The Japanese maker Yamaha brought it wide circulation with the DX7 synthesizer of 1983, and sounds such as electric piano, bells, and basses of the 1980s are strongly marked by it. Today FM synthesis is found in numerous software and hardware synthesizers.
FM synthesis should be distinguished from subtractive synthesis, which shapes sounds from overtone-rich waves with filters, and from the sampler, which plays back recorded sounds. It also differs from vibrato: in vibrato the pitch varies slowly, in FM synthesis fast and in the audible range, so that a new tone color arises.
Performance practice
In FM synthesis, experiment with the ratio of the carrier and modulator frequencies: whole-number ratios give harmonic sounds, others bell-like inharmonic ones. Change the amount of modulation and observe how the sound gets brighter or duller.