Yamaha MU128 Owner's Manual page 168

Initialize Functions (INITIAL)
Drum (DrumInit)
Range:
This restores the original drum settings for the selected Drum Setup
S1 — S4. (Use the VALUE -/+ buttons or data dial to select the
desired Drum Setup.)
NOTE
This parameter is not available when the MU128 is set to Performance mode.
3 From the "Are you sure?" prompt, press the ENTER button to execute
the operation, or press the EXIT button to cancel it and return to
the previous display.
An "Executing..." message appears in the display during the
operation. When the operation is completed, the MU128 returns
to the Initialize menu.
168
DrumS1 — DrumS4
MU128 Utility Mode