squeak D...Basically BIAB will do all that is in your question...its a great program. The latest version is ver11 but even from ver9 which I use they included an excellent Solo Improvisation feature. The help file is extensive so print it out and get eyes reading.
The most impressive feature for me is you can knock up a song and save it as Midi File within 10 minutes with Drums,Bass and all ACC tracks. Also the printout is the best quality you will obtain of any sequencing program.

Happy programming...Graham UK