Yamaha TG500 Owner's Manual page 156

VOICE EDIT MODE / 3: Full Edit. 3-6: Controller
PtBs (Pitch bias depth)
144 3-6-02: AFTER TOUCH DEPTH
Range: -12 ... +12
Sets the maximum pitch variation range achievable via after-touch control.
Each increment represents a semitone. A setting of "0" produces no pitch
variation. A setting of "+12" allows a maximum pitch variation of one octave
up, while a setting of "-12" allows a maximum pitch variation of one octave
down corresponding to aftertouch key pressure.