Yamaha MU128 Owner's Manual page 167

Factory Settings (FactSet)
This restores the original factory settings of the MU128.
Selected Sound Module Mode:
Extended General MIDI (XG Init)
General MIDI (GM Init)
Performance (PFMInit)
One of the three parameters above will be available, depending
on the currently selected Sound Module mode: XG, TG300B or
PFM. Initializing this parameter restores the original settings for
the selected mode.
NOTE
For the PFMInit setting, only the currently selected Performance will be initial-
ized.
MU128 Utility Mode
Initialize Functions (INITIAL)
167