Yamaha TG500 Owner's Manual page 133

VOICE EDIT MODE / 3: Full Edit. 3-3: Filter
The "BEF" (Band Elimination Filter) setting produces a filter response that
eliminates a band of frequencies centered at the cutoff frequency (See "Cutoff"
below) to pass. The "Band" parameter (below) determines the width of the
elimination band.
3-3-01: PARAMETER
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