i know i'm notorious for recommending RealBand but humour me. open the midi file in RB. each track is clearly separated and obviously available for you to work on.

just try it. unless one of the BIAB gurus can say different, I'm not aware of anything you can't do in RB that you could in BIAB - and i think there's a lot more.

analyse the chords and you can add RTs, new midi instruments,change key, change tempo and edit midi parts.

and all on separate tracks you can see.

and if i remember from separate posts you don't have a good midi soft synth. get the TTS-1 free from Bandlab - see Peter Gannon's no brainer post.