The Gracenote Rhythm API allows developers to integrate radio and music recommendation features into web services. Requests and responses are available in XML, REST, and JSON formats. Authentication is possible with Key. In the endpoint, developers can replace 1234567 for their Client ID. The main characteristics of the API include adaptive radio, playlist, feedback, and rich content. It supports regulation provided by the Digital Millenium Copyright Act. Gracenote (formerly CDDB) maintains and licenses a database of audio CD information, digital file identifications and song lyrics.