FM synthesis generates harmonic spectra when the modulating frequency equals the carrier frequency

Evidence

Perhaps the best-known example of non-linear synthesis is FM synthesis (Chowning, 1977), where a parameter of the carrier oscillator is modulated with another oscillator(s). Its basic form uses simple frequency modulation, such as y(t) = sin[ωct + sin(ωm)t], to form a spectrum with peaks at frequencies ωc ± nωm. If ωc = ωm, a harmonic spectrum is produced with the fundamental frequency f0 = 2πωm, which can be used in music sound synthesis. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 692

Categorization

• XREF: FM synthesis is the classic sound-generation method behind 80s synthesizers and early video game music; connects to sound design practice.
• corroborated: 2 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 692