The encoding of a carrier wave by variation of its frequency in accordance with an input signal.
An outdated data encoding scheme. This technology used up to half of the disk space with timing information for the encoding process and was replaced with better standard called MFM.
Frequency modulation allows the output of one oscillator to drive the frequency of another oscillator. It can generate very complex sounds from very simple waveforms and is the basis of the Yamaha DX range of synthisizers and OPL range of synthesizer chips (used in Adlib and most other soundcards).