Google Music is rumored for quite some time now. Now, its not just a rumor. Google has just added "/music" to its robots.txt file. So, all it means is Google music is getting real close. It is not so easy to predict any file name present in that directory and I never got any time for it too. Try yourself and let me know if you get some clue.

Disallow: /music

in the robots.txt file, google has disallowed crawlers for /music directory like they always do for each of there projects.