Yamaha P-100 Owner's Manual page 52

Whenever the P-100 receives a program change message, it will check the program change receive table to determine
whether a voice has been assigned to the received program change number. If so, the main voice will automatically
switch to the voice indicated by the program change receive table. (If the P-100 is in Dual mode, this will cause it to
shift to Single mode.) If the program change function has been turned off for that number, the message will simply be
ignored.
Keep in mind that the assignments you make in the program change receive table are only valid as long as a channel
has been selected as the program change receive channel. The procedure for selecting a program change receive
channel is described on pages 32 and 33.
4. Exit MIDI Utility mode.
Press the [MIDI] button to exit MIDI Utility mode. (If you
wish, you can return to step 2 to change other settings before
you leave this mode.)
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