Yamaha P-100 Owner's Manual page 37

SPLIT MODE
The situation becomes more complex in Split mode. Since the two timbres play independently rather than in unison,
two MIDI channels are needed to control them. For this reason, the P-100 divides its keyboard into two areas, known
as the main and sub keyboard areas. Channel voice messages from the main keyboard area are sent to the main voice
and output on the transmit channel (Tch) as in Single mode. Messages from the sub keyboard area are sent to the sub
voice and output using the next higher MIDI channel (Tch+l). Since the P-100 thus outputs its messages on two MIDI
channels in Split mode, you can use the P-100's keyboard in this mode to control two of an external tone generator's
timbres.
Data received at the MIDI IN terminal is handled in the same manner: channel voice messages on the receive channel
(Rch) are sent to the main voice, whereas messages on the next channel up (Rch+l) are sent to the sub voice.
In any of the P-100's three modes, you can turn off the connection between the P-100's keyboard and tone generator
sections by setting the local control function off. Doing so will stop the P-100's tone generator from responding to
notes played on the keyboard, however, the keyboard will still transmit messages via the MIDI OUT terminal, and the
tone generator will respond to messages received at MIDI IN. The procedure for turning off the local control function
is described in the next chapter.
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