I think you have to put chords into either BIAB or RB to give the RTs something to generate to........as far as i'm aware you can't just play RTs. mind you if you tried putting just one chord in and not changing it but maybe adding part markers to break things up then the RTs might create a non-groove track. try it. not sure if you could play and record notes from your midi keyboard in RB and then use the playable RTs - but you could certainly do it with midi