Yamaha TG500 Owner's Manual page 207

DRUM VOICE COMPARE
[EDIT/COMPARE]
The drum voice compare function makes it possible to compare the sound of a
drum voice being edited with the same drum voice prior to editing.
To temporarily recall the original drum voice data while editing, press the
[EDIT/COMPARE] key. The [EDIT] LED will flash, indicating that the compare
mode is engaged. Press [EDIT/COMPARE] a second time to return to the edit mode
and the drum voice being edited.
DRUM VOICE EDIT MODE / 5: Recall/Init.
DRUM VOICE COMPARE
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