Approximate spectrum
frequency →Relative amplitude · components up to 6000 Hz
SYNTHESIS · 03
FM synthesis.
Use one oscillator to modulate the frequency of another. Relate what you hear to the sidebands appearing in the spectrum.
Playback
Harmonic FM
SHAPE THE TIMBRE
Carrier, modulator and index
An integer ratio aligns the sidebands with a harmonic series.
c220 Hzm440 HzΔf = I·m1760 Hz
Waveform
time →WHAT IS HAPPENING
Two oscillators can create a complex spectrum.
The modulator continuously changes the instantaneous frequency of the carrier. With a slow modulator, we hear vibrato.
The index relates frequency deviation to the modulator frequency. Increasing it produces more sidebands.
Integer ratios tend to produce harmonic spectra. Non-integer ratios shift the sidebands and produce metallic or bell-like timbres.