Try the last.fm api at http://www.last.fm/api.
If that doesn’t work for you, you can look at the various APIs listed in this search result:
http://www.programmableweb.com/category/music/api
This is a Silverlight tutorial, but since this is an HTTP REST API, it could seem agnostic to you to get started: http://www.devx.com/VisualStudio/Article/40158.