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Yamaha FM Synthesis Manual page 3

the FM model: With only two pure sine waves a new complex waveform

is obtained which consist of many newly formed sinusoidal vibrations,

caused by the modulation principle (see fgure below from the

DX7

manual).

The importance of this is further underlined by the fact that every

conceivable sound is made up of a plurality of sinusoidal vibrations,

with corresponding frequency, amplitude and phase. The sinusoidal

vibration with the lowest frequency is the frst harmonic or

fundamental. The higher frequencies are called overtones or

harmonics. One such pair of operators with sinusoidal waveforms, the

carrier and the modulator is in the electronic and computer music

language is called simple FM.

timbre

the frequency ratio between carrier and modulator: determines

which overtones can be obtained.

In musical terms: the pitch interval between the modulator and carrier

controls which harmonics or overtones can be formed.

In a way we may compare the c : m ratio in FM synthesis with the

type of oscillator waveform in subtractive synthesis

the amount of frequency modulation determines the amount and

strength of the overtones