As of now, Google Music Beta is just like Google+ since people can only avail of its service through invitation. If no one invited you in then, you can not take advantage of the features that Google Music is offering their users.
Unlike Google+, it does not have any app to help the users out. However, there is the HTML5 Web interface, which makes playing songs in your Google Music locker look like a snap. It is a terrifically Google-like solution, although, sarcastically, Google creates an Android app for the service.