Korg prologue Owner's Manual page 23

PANEL switch (prologue-16 only)
Sets the timbre to edit.
SUB: Edits the sub-timbre.
+ (MAIN+SUB): Edits both the main and sub-timbres.
MAIN: Edits the main timbre.
This is set in "Edit Timbre" (p.46) in PROGRAM EDIT mode on the prologue-8.
Editing a timbre applies to the basic parameters on the front panel, as well
TIP
as all detailed parameters in PROGRAM EDIT mode.
[SUB, +, MAIN]
23