I would doubt that Yamaha uses only one channel for a backing track. Drums will be on Channel 10 and piano etc on other channels. 
If it even outputs the midi data at all. Some don't. 
But there is a CAL script that will seperate the channels. 

You're better off asking on the Motifator forums. This is more a question with the setup of the MOXF. Not sure it's possible to do.

Select the track and from the Process Menu select Cal split notes to tracks. Make sure that the track containing the midi is the last track

A custom CAL is all I can think of unless the hardware can have the output adjusted (never used one, but would seem probable). If the splits are static, is one CAL; but if dynamic, I would hunt for a hardware output setting.

From a very brief reading of the MOXF8 manual: In performance mode, the MOXF8 separates parts by note range and velocity range, rather than channel. In Sonar, it is easy to select notes by value or range. Velocity range can be selected by the more complex "Edit > Select > By Filter".
 
Arpeggios are emitted on the MIDI output if selected by the Output Switch. Looks like the channel for arpeggio output can be set to something other than the keyboard channel.

It occurs to me that you have not made clear what it is you are trying to do since "part" is an ambiguous term here. Sometimes it is used to mean the difference between the notes played by the right hand and the left hand in a keyboard piece. There is no way for software to know which hand is playing what note (although it can guess) based on the pitches. Sometimes it means the notes played by each instrument in an arrangement for several instruments. That latter is usually done in MIDI by recording the tracks individually, one for each voice/patch/instrument at a time, each to its own track. It is possible to create keyboard "splits" on some keyboard synths that will produce different voices from different keys using the built in synthesizer, but that is done with onboard logic routing not MIDI. It would be very unusual to be able to use the MIDI capability of a keyboard to send splits as MIDI to a DAW, although it could conceivably be done by associating each key of the split with a patch change message or sending each split region out as a single midi channel. If your keyboard cannot separate out splits in the MIDI data it sends out, then all the MIDI data will be merged in its output, but you could still separate out the splits after recording the merged MIDI output by applying filters based on note numbers to the recorded MIDI track and manually creating your own tracks.
 
"Dissolve parts" in Cubase will let you separate a multi-channel midi file into separate channels one for each track/lane, or it will let you separate individual pitches (MIDI note values) into their own lanes. The former is only useful if you have a MIDI file coded to contain multiple tracks in a single file. The latter is almost exclusively useful if you want to separate a drum track (where each note is a separate instrument) into separate tracks/lanes for each instrument. If what you want to do is separate parts of a keyboard performance where each note is a separate note on the same instrument, say in order to split the right hand from the left hand part, that feature would give you a separate lane for each note not for each part. That would give you a couple of dozen different tracks/lanes one for each keyboard note, and is probably not what you want.
 
 

@joden
Let me know if you figure it out. . . I have a MOX8 and this would be useful.  I have a love/hate relationship with Performance Mode. . . if they just added a few more features it would be so much better.

Mystic38
..........and there are videos about setting up Sonar with Motif (actually its one of mine) and there are notes on Yamaha support site about editor setup with Sonar.
 
hth

 
Could you provide a link please?

jeez Sir Les - why on earth did you think that would be useful? Been using and manipulating MIDI for 25 years...the thread is about how to strip down Motif arps which are all played on a single MIDI channel (four parts at once) into separate tracks without a mountina of work to determine what note belongs to what instrument, and pitch and velocity mean nothing as all the tracks have verying pitches and velocities.
 
Simple answer is it cannot be done simply so the best solution is to just record it to the onboard sequencer and then save that as a midi file and then try to work on that...MAYBE master mode (or song mode) might allow further identification, I don't know at this stage.

The link provided by Les is one to Noteworty Composer and describes the difference between type 0,1 midi files???
 
However YOUR link mettelus is correct, thanks. Although it is fro setting up the VST in X3, I am running Platinum and I already have the VST3 setup and working. Again, this is not the focus of the thread. Seems to be everything but
 

You know we are trying to help and your coming back with " I know everything already so don't tell me this". We don't know how much or how little you know about midi. Most people these days don't.  In my 30 years of working with midi and sound modules I've never ran across one that would use 1 channel to trigger all instruments?? Seems screwball to me,,. So now I will know in the future that such a beast does exsist.  
 
Seems Mystic 38 has a good solution. 

Thanks VB - never knew that site existed...good tip!
 
@Cactus - never said I knew everything, just trying to figure what the hell a link describing midi format 0/1 files was for?! fwiw I agree re the four parts to one channel thing (only in performance mode) , but that's how it is and I just have to learn to deal with it. Just thought with the number of years this Motif arp system has been around, that a Sonar user might have some learned tricks they could pass on. No biggie if there isn't.

Probably just my old head mystic38, but I just don't get exactly how one gets the four parts of a performance to export via midi to the PC to four separate tracks..when I use a master to store the perf all four parts still transmit on channel 1 so the end result (at the PC end) is still the same....the need to sort through every note to determine whihc instrument it is to be playing. The workaround I am using is to turn off all but one part, play through the song to record that part...then turn it off and move to the next part....rinse and repeat. Takes a while, but I think it would take me longer to figure out the steps needed to go the other way

Trying to use the performances for putting down songs into Sonar....

thanks vb I will research Pattern Mode some more and try the editor as well...