Yamaha MONTAGE M6 Operation Manual page 385

Resonance (Spectral Resonance)
Sets the sensitivity of the resonance effect in Spectral.
The center frequency will be shifted to higher-order harmonics, so you can create the
resonance effect or add special characteristics to the sound.
This parameter is available only when Spectral is set to Res 1 or Res 2.
Settings: 0–99
Sine is a simple waveform containing only the fundamental wave with no harmonics, while other
waveforms contain harmonic overtones. Therefore, when you have set Form to a wave other
than Sine, the parameters related to the harmonics and its "peak" values (formants) will be
available. Below are some specific parameters for controlling each wave explained in Spectral.
You can increase the number of harmonic overtones by setting a larger Skirt value to expand
the spectrum range.
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