Yeah, that's what's not so great about the medley thing... each soloist will play through the entire tune so you'd have to have 2 or 3 'chorusus' meaning the tune would play 3 times through, each time with a different soloist.

Sounds more like you want to have, say, a piano for bars 13-20, then a sax at bar 33-40 etc. right ? If that's what you want to do, then Real Band is your tool for that.