jag,
there are plenty of programs out there that can easily remove certain instrument and vocal frequncies from MP3s or any other sound type.
I sometimes manually edit them with an equalizer with Sound Forge (which costs a lost). There are some shareware programs out there that can do the same thing like "Transcribe!" and "GoldWave." There is also another one out called "Karaoke Maker" and "DeComposer," but those cost around $40, or $100 in a pack with another program.
I use this a lot to write tabs for songs, or just to learn certain solos so I can play them along with my friends. Search for these programs on Google or Yahoo and you are definately going to turn something up. Have fun.
