Indaba, a music creation/collaboration platform, is open to any band with the capital to join. The service already has 600,000 registered users, and now Grooveshark is tapping into those indie bands to provide entertainment for its 30 million monthly unique visitors. Indaba members need only to submit music via the site to be considered for inclusion in Breakthrough Radio.
Yes, musicians can submit their music to other streaming/subscription services, like Pandora and MOG (which pulls in music via distributors). But the fact that Grooveshark is working with Indaba will likely make this a much more straightforward experience for bands -- and will likely bring more bands into the Indaba fold.
This isn't the first time a music service has focused on up-and-coming bands -- startup EarBits draws solely from that well. But Grooveshark is an extremely popular service, so this is a good move for musicians.
Keep in mind, however, that Grooveshark's iPhone and Android apps have been booted from their respective stores due to record label complaints, which does significantly limit the potential number of listeners.