Software that breaks MP3s down into their component instruments

[64Guitars]

This could be a useful tool for learning songs if it works as they describe it.

http://www.bbc.co.uk/news/technology-12510702

http://www.hitnmix.com/

The free version doesn't let you adjust the levels of the individual instruments, but it does let you delete them. So you should be able to delete everything but the guitar, for example, to learn how to play a difficult solo. Unfortunately, the free version only works for 30 days and the full version costs $119.99 US or £71. 

I might download the free version and try it out.

[Oldrottenhead]

some video in this link looks pretty impressive http://www.bbc.co.uk/news/technology-12070508