Frequency modulation synthesis

Frequency modulation synthesis (or FM synthesis) is a form of sound synthesis whereby the frequency of a waveform is changed by modulating its frequency with a modulating source known as an operator. The (instantaneous) frequency of an oscillator is altered in accordance with the amplitude of a modulating signal.

Developed in the 1960s by researchers at Stanford University, then commercialized through digital instruments such as the Yamaha GS-1 and popularized by the Yamaha DX7 in the 1980s, FM synthesis has had a lasting influence on recorded music, electronic music, popular music, and video game music. It became closely associated with the sound of the 1980s, while related Yamaha FM chips gave many arcade games, home computers, game consoles, sound cards, and early mobile phone ringtones their characteristic timbres.

Its spread from Stanford University computer-music research into studios, homes, arcades, and consumer devices has made FM synthesis one of the most widely heard forms of digital synthesis of the late-20th century.