Editing Frequency modulation synthesis (section)

{{short description|Form of sound synthesis}}
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|+ '''FM synthesis using 2 operators'''
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|style="line-height:1.8ex;text-align:left;"|<small>[[Image:2op FM (large font).svg|left|200px]] A 220&nbsp;Hz carrier tone ''f<sub>c</sub>'' modulated by a 440&nbsp;Hz modulating tone ''f<sub>m</sub>'', with various choices of [[frequency modulation#Modulation index|frequency modulation index]], ''β''. The time domain signals are illustrated above, and the corresponding spectra are shown below (spectrum amplitudes in [[decibel|dB]]).</small>
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; Waveforms for each ''&beta;'':
[[Image:frequencymodulationdemo-td.png]]
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; Spectra for each ''&beta;'':
[[Image:frequencymodulationdemo-fd.png]]
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'''Frequency modulation synthesis''' (or '''FM synthesis''') is a form of [[Synthesizer#Sound synthesis|sound synthesis]] whereby the frequency of a [[waveform]] is changed by [[Frequency modulation|modulating its frequency]] with a modulator. The [[instantaneous frequency|(instantaneous) frequency]] of an oscillator is altered in accordance with the [[amplitude]] of a modulating signal.<ref>{{harvnb|Dodge|Jerse|1997|p=115}}</ref>

FM synthesis can create both harmonic and [[Inharmonicity|inharmonic]] sounds. To synthesize harmonic sounds, the modulating signal must have a [[harmonic]] 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.

FM synthesis using analog [[oscillator]]s may result in pitch instability.<ref>{{Cite book |last1=McGuire |first1=Sam |url=https://books.google.com/books?id=S90NEAAAQBAJ&dq=analog+fm+synthesis+unstable&pg=SA3-PA11 |title=The Art of Digital Orchestration |last2=Matějů |first2=Zbyněk |date=2020-12-28 |publisher=CRC Press |isbn=978-1-000-28699-1 |language=en}}</ref> However, FM synthesis can also be implemented digitally, which is more stable and became standard practice.