Disklavier

I'm on a Macintosh. And I often find wonderful sequences of piano music
which I can play through my computer to the Disklavier, but sometimes I
can't get the right tracks to play. 

Is there a way to:

    set the piano to play all tracks? (treble and bass?)

    find a midi sequencer that's shareware and simple enough to figure out
how to transfer notes from one track to the other?

Thanks

Best wishes to all for the New Year!