Something awesome is happening in the world of music and the web. But first, some primer.
Rdio is one of the few music subscription services that do a tremendous amount of things right, including having its robust Rdio API. For $5 a month, you can get all of the music you want, have collaborative playlists, share content to Facebook and Twitter, and keep up with what your friends are listening to. For $10, you can do all that and store the music to your phone for offline or higher quality enjoyment.
The Independent Online Distribution Alliance (IODA) has just announced its IODA Open API, currently in beta. The API offers many of the typical resources that you would expect from a music metadata service, with a few extra goodies like these album attributes: UPC code and primary label. Comparing album API results between IODA Open and iTunes, IODA is packing a lot more information into the response.