Frequency modulation synthesis

FM synthesis using 2 operators<table><tbody><tr><td> A 220 Hz carrier tone <i>fc</i> modulated by a 440 Hz modulating tone <i>fm</i>, with various choices of <a href="/facts/Frequency_modulation/qIExDdtv">frequency modulation index</a>, <i>β</i>. The time domain signals are illustrated above, and the corresponding spectra are shown below (spectrum amplitudes in <a href="/facts/Decibel/0LyxAPXh">dB</a>).</td></tr><tr><td>Waveforms for each <i>β</i></td></tr><tr><td>Spectra for each <i>β</i></td></tr></tbody></table>
<p>Frequency modulation synthesis (or FM synthesis) is a form of <a href="/facts/Synthesizer/NrmdVrPa">sound synthesis</a> whereby the frequency of a <a href="/facts/Waveform/yAskMREw">waveform</a> is changed by <a href="/facts/Frequency_modulation/qIExDdtv">modulating its frequency</a> with a modulator. The <a href="/facts/Instantaneous_frequency/fJ17zuan">(instantaneous) frequency</a> of an oscillator is altered in accordance with the <a href="/facts/Amplitude/aEckuXJM">amplitude</a> of a modulating signal.
</p><p>FM synthesis can create both harmonic and <a href="/facts/Inharmonicity/xDSTCe95">inharmonic</a> sounds. To synthesize harmonic sounds, the modulating signal must have a <a href="/facts/Harmonic/9U9REzeR">harmonic</a> relationship to the original carrier signal. As the amount of frequency modulation increases, the sound grows progressively complex. Through the use of modulators with frequencies that are non-integer multiples of the carrier signal (i.e. inharmonic), inharmonic bell-like and percussive spectra can be created.
</p><p>FM synthesis using analog <a href="/facts/Oscillator/6vSrm84a">oscillators</a> may result in pitch instability. However, FM synthesis can also be implemented digitally, which is more stable and became standard practice.
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Frequency modulation synthesis open-in-new

Frequency modulation synthesis