Yamaha PortaTone PSR-172 Owner's Manual page 59

MIDI Implementation Chart
NOTE:
*1 Playing the keyboard does not produce any changes in velocity data; the
transmitted velocity value is fixed. The velocity value generated by playing
the key is predetermined for each voice and may differ depending on the
selected voice.
*2 MSB can be used to change the voice for the Melody or Rhythm.
MSB=00H :Melody Voice
MSB=7FH : Rhythm Voice
LSB: Refer to Voice list.
*3 For program change values, refer to the voice list.
Program change and other like channel messages received will not affect
the PSR-160 panel settings or what is being played on the keyboard.
*4 < GM System on > F0H,7EH,7FH, 09H, 01H, F7H
All data is restored to the default values.
*5 MIDI does not function (transmit/receive) in the Song mode.
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