Help Making a Backing Track

[macmeda]

I used to play with a guy who would take different tracks out of a pre-recoded piece of music and we would use them as backing tracks. Like delete everything but drums and bass. How can I do that , and can I do it to professional recordings I've purchased say on itunes or a cd?

Thanks
Mac

[UnderTheGroove]

There isn't any way to effectively remove a single instrument from a stereo track like you would get on itunes or a CD. Is it possible your friend had the multi-track mixes for the music he was using? Or he may have been using MIDI files?