Harmonically complex FM waveforms (saws, squares) generate richer inharmonic sidebands than sines for percussion

In FM synthesis, the modulator waveform determines which sidebands appear in the output. A sine modulator creates sidebands at carrier ± n*modulator (for integer n); more complex waveforms add higher harmonics that generate additional, more densely packed sideband clusters. For metallic percussion, dense inharmonic sidebands are desirable — they fill the frequency range with texture rather than discrete tones. Saws and squares, containing many harmonics, produce richer and denser sideband spectra than sines. Conversely, when FM is used for clean, musical tones (DX7-style), sine modulators are preferred precisely because they produce fewer, more controlled sidebands. This waveform choice is therefore a deliberate timbral decision.

Examples

Try FM hi-hat patch with: (1) sine modulator — relatively sparse, somewhat tonal output; (2) square modulator — dense, buzzy metallic output; (3) saw modulator — asymmetric, bright metallic output. Compare against white noise.

Assessment

Patch the same FM hi-hat with three modulator waveforms (sine, triangle, square), filter with the same HPF cutoff, and describe what changes. Explain the spectral mechanism for each difference.