BTW Sony and philips already have something like this implemented in some of the music players and it appears to work pretty well. So it's not science fiction :) Sadly there's nothing available in Open Source.
http://users.skynet.be/solaris/linuxaudio/
Send this dude some e-mail. I bet he will have some really good insight on your auto classification request. His Perceptual Analyser might even be a starting point.