Last.fm is a music-listening service that provides recommendations based on user preferences. Rikki Tooley created an SDK in .NET language with the main goal to offer functionality beyond API bindings. This kit is supported in .NET Framework 4.5, Windows 8.0, Windows Phone 8.1, and Windows Phone Silverlight 8. A quickstart guide is available with installation, usage, dependency, and planned features. One of the future plans is to improve identification of poorly tagged tracks using audio fingerprints and the MusicBrainz API. Because music lovers can benefit from the improvement of this feature, Rikki Tooley invites other developers to join the conversation on https://gitter.im/inflatablefriends/lastfm
Yes.com is a unique community-oriented music site that provides real-time and historical information about songs played on United States terrestrial radio stations. Besides this up-to-the-minute database, Yes has social features like chat rooms for specific radio stations or for a specific artists, like the Yes.com Pink Floyd page showing which radio stations are currently playing or recently played Pink Floyd songs. In addition they also offer an API that developers can build on (our Yes API profile).
ProgrammableWeb lists many popular Music APIs in the directory including Last.fm, 7digital and Spotify Metadata. This post features a few really creative, entertaining mashups that use a few popular Music APIs.