Sun Labs are currently working on a research project to investigate the possibility of searching for music, not just by track and group, but by the actual ‘content’ of the music.
This is a facinating idea, as I’ve often wondered how it would be possible to be able to search for other songs that sound like this particular song that I like. The Sun project is analyszing characteristics in the sound so that comparisons can be made between other songs to find simularities.