Peachnote is quite an innovative approach to music analysis. Developed by Vladimir Viro, a renaissance man who bridges the worlds of classical music and advanced mathematics, the Peachnote API provides the ability to search a large collection of public compositions by melody or sequence of chords.
Shoutcast maintains a radio directory of 50,000+ radio stations from all around the world. The company, owned by AOL, released its first Shoutcast API a few years ago, but has since released version 2.0. The updated API provides developers with more advanced options for integrating music streaming services into web services and mobile applications using RESTful calls formatted in XML, JSON and RSS.