Yamaha Motif DDK-7 Owner's Manual page 106

Song Part Information
Pressing the [PART SETUP] button calls up the Part Setup display of the currently
selected song, letting you confirm which parts are played when playing the song.
When playing back the song (by pressing the [F] button), only those parts that
are set to "PLAY" in the Part Setup display actually play, while parts that are set to
"OFF" are muted. (If the song contains no performance data, all parts are set to
"OFF".) You can change the status for each part by changing the PLAY/OFF
settings for each part and pressing the [SAVE] button in the display.
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