With the new service, your music and playlists are automatically kept in sync, so if you create a new playlist on your phone, it’s instantly available on your computer or tablet. You can use a feature called Instant Mix to create a playlist of songs that go well together. You can even listen to music when you’re offline: we automatically store your most recently played music on your Android device and you can choose to make specific albums or playlists available when you’re not connected. The service is launching in beta today to U.S. users and is available by invitation.
To find out more info and to apply for the beta visit Music.Google.com.