CD-R's work well in my case. Arrange the tunes on an arranger keyboard, or Band In A Box, bounce to a 16-track recorder. Add appropriate overdubs---strings, choral oohs and aahs, extra percussion, etc.. Burn to CD and presto, personalized backing tracks for solo guitar/vocals. Works great if you're careful about your bookings. Obviously, it's tough to play requests if they're not on the CD.