But for now, it's only in the USA. Just like Google Books.
As the Google blog puts it:
Music Beta enabled you to upload your personal music collection (up to 20,000 songs) for free to the cloud so you could stream it anywhere, any time. Today, the beta service evolves into a broader platform: Google Music...
With the Google Music artist hub, any artist who has all the necessary rights can distribute his or her own music on our platform, and use the artist hub interface to build an artist page, upload original tracks, set prices and sell content directly to fans—essentially becoming the manager of their own far-reaching music store. This goes for new artists as well as established independent artists, like Tiesto, who debuts a new single on Google Music today.
Read more at the Google Blog