Hi Ed

By taking your song into Realband (comes free with BIAB)and doing some cutting and pasting with the Realtracks and your own input you can "sort of" create your own custom Realtrack.

Give Realband a try and with the help of the good people in these forums you'll find it opens up a whole lot of possibilities for customizing your songs the way you want to hear them.

Also check out the very informative user videos posted here and on youtube.
You'll learn a lot and have fun along the way.

http://www.pgmusic.com/videos.user.htm

Enjoy the ride.
Carkins