The Rdio iOS SDK by Rdio allows API interaction via a native playback implementation. With the SDK, developers can make calls, authenticate users, and stream audio. Available framework, documentation, and a getting started guide.
For staying up to date with band tour dates, live venue information and more, Pollstar has it covered. It's a trade publication that covers music industry information on a worldwide scale. What's pretty cool is that Pollstar provides an API that allows third party developers access to the full event database, enabling them to include Pollstar data on other websites and applications.
Stitcher; the mobile leader in news, entertainment, sports, and talk radio; recently released Stitcher Connect. Stitcher Connect is "talk radio's first API developed for the car." The API delivers all of the features of Stitcher's mobile app (Stitcher Smart Radio) directly to the vehicle. According to Stitcher CEO, Noah Shanok, "Over a third of our listeners are currently using Stitcher in the car [via the mobile app]." The next logical step was to integrate directly with the automobile, so "listeners can seamlessly access and discover the best of over 10,000 shows on Stitcher in the car."