Hi there Vernon
I suppose it's really a matter of what sort of quality you're after, if it's backing tracks of 'recording' quality to incorporate in your projects I expect a search will find many a studio or musicians prepared to supply this service but it's unlikely to be free.
Another method might be to invest in something like
Guitar Tab Pro - typically a tab will include the guitar parts, often the bass guitar and sometimes a drum track. You can export the MIDI information and then play your own softsynth presets using this information. This method's big drawback is that it's only any good for cover songs.
A program which will let you input your own arrangements is Band-In-A-Box - I know the latest version is reported to be capable of creating some decent quality backing tracks and I know quite a few of the guys use it to compose with.
Another way to put together just what you want would be to maybe post in the Songs Forum asking if anyone fancies recording a collaboration project with you - once you've given a few details of the song and the parts you need covered, or even by posting a 'scratch track' of what it will sound like, you should get some offers of help and away you go!
Hope that helps
Steve
post edited by SteveStrummerUK - 2008/09/27 20:56:22