This may be obvious to some, but how do I tell the XP80 that in one midi file I want to play chanel 5 part and on another I want to play the chanel 2 part, etc. Is there a control I can write into the midi file. Up to now I've been juggling the instruments so that it's always channel 1 which is the part I play.

Do you mean so that it will automatically select the part you want when you open a midi file? As far as I know there isn't a feature like that, you'll just have to do it manually.

is that something with changing the channel on your setting?

The other way of doing it is copying those data to other tracks and assgining the patch. this will free up the channel you want to use.