You can get software I think that removes vocals so you can turn your CD collection into MP3 backing tracks. I've never used them, but I believe they are good at removing around 90% of the vocals. I think it works by filtering out the frequencies that are occupied by vocals, which is the range 3Hz to 3kHz. The only thing I don't really understand is how they only remove vocals when a lot of instruments also occupy those frequencies. Therefore I think you might lose some quality or it may not do some songs too well, but you'll have to give it a whirl. You can download some software here; http://www.hitsquad.com/smm/programs/YoGenVocalRemover/, it also tells you a little more about it. Good luck.