Amazon introduced a music streaming feature on Thursday called Prime Music. It gives subscribers to its Prime service access to thousands of songs free and without interruptions from advertising. What will the authors get for the use of their copyrights? That's still totally unknown. Amazon offered the record companies a royalty pool, to be divided by a market-share formula of Amazon’s choosing. Sony and Warner Music have signed such deals. Universal, whose catalog includes stars like Lady Gaga, Katy Perry and Kanye West, did not reach an agreement with Amazon. After contracts for songwriting rights were rejected by many music publishers, Amazon used an outside firm to obtain “compulsory” licenses through federal copyright provisions. Prime Music is not seen as a major threat to companies like Spotify, Rhapsody and Beats Music. But Amazon’s sheer size gives it a big advantage.