All the Keyboards with rhythem play good bass lines. (Even the cheap toy ones.)
Roland has rom modules for different styles on thiers.
Technics has a new gadget that can build bass lines on the lowest
note of your chord voicings. This gadget, the 3000 is, ~$4000 bucks. That
gadget can probably put its bass lines on midi.
I have a Yamaha qy20 sequencer on which I can record electric sax solos and
then file them away on a floppy disk. The qy20 will also allow you to do
what you suggest for band in a box. I could put in anybody's chord
substitution chart and try to play over it. The result will be the essance
of the work.
I would like to send my midi stuff to your group so they can hear me play.
Anyone who has a qy20 can read my files. Is this feasible?