Yamaha QY100 Owner's Manual page 140

The Song Voice Mode
Filter Controls
The filter controls affect the basic "timbre" of the sound.
Resonance
Cutoff Frequency
CUT (Cutoff Frequency)
Sets the cutoff frequency of the low-pass filter from "-64"
through "0" to "+63". Negative values lower the cutoff fre-
quency, producing a "darker" sound. Positive values raise the
cutoff frequency, producing a brighter sound. The graphic filter
response curve will shift to indicate the current setting (the
heavy default setting curve will also remain on the display).
RES (Resonance)
Adjusts the height of the filter's resonance peak from "-64"
through "0" to "+63". Negative values lower the resonant
peak producing a "flatter" sound. Positive values increase the
resonant peak, emphasizing components at the filter cutoff
frequency. The peak on the graphic filter response curve will
grow or shrink to indicate the current setting (the heavy
default setting curve will also remain on the display).
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