What exactly do you mean by chords and rhythm? Everything is chord based in BIAB except the drums and many things can be classified as a rhythm instrument with BIAB. So a little more detail would help. That said, if you have a version of BIAB that allows it, the Bar Settings (F5) will let you set rest (called mutes there) or lower volumes, etc. and has an option to apply it to specific choruses. Maybe that will give you a place to start.
Good luck.