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.
The Take.io API from Brazil has a REST protocol with data formats in XML and JSON. According to Take.net, "The take.io RESTful API currently defines five services: SSO, Core, Billing, Messages and Reports." The company states further that, "Take.io is Take.net DNA translated into a set of APIs designed to allow companies to use SMS, MMS, voice, pricing, location, CRM, etc., all of which are integrated with their existing systems."
The legendary Billboard charts are now open for mixing, not by DJs, but by programmers. Billboard, a service of Nielsen Business Media, has a new API that lets developers search and read information from all the Billboard historical charts. The initial offering is its Chart service and later on Billboard will "roll out the Artist and Track services to add even more depth and perspective." the API is a simple REST interface that developers can send HTTP GET requests to in a familiar service/version/resource fashion. We've added a new Billboard API profile with details.