EN (which powers the Rdio create station feature that rolled out recently) has similarity data and popularity data for songs & artists natively. Popularity of

EN (which powers the Rdio create station feature that rolled out recently) has similarity data and popularity data for songs & artists natively. Popularity of a single song: http://developer.echonest.com/api/v4/song/search?api_key=FILDTEOIK2HBORODV&format=json&results=1&artist=radiohead&title=karma%20police&bucket=song_hotttnesss http://developer.echonest.com/api/v4/song/search?api_key=FIL... List of songs by an artist ordered by popularity http://developer.echonest.com/api/v4/song/search?api_key=FILDTEOIK2HBORODV&format=json&results=10&artist=radiohead&bucket=song_hotttnesss&sort=song_hotttnesss-desc http://developer.echonest.com/api/v4/song/search?api_key=FIL... Since we have Rdio in our Rosetta ID space, you can natively use Rdio IDs and get them back in your calls: http://developer.echonest.com/api/v4/song/search?api_key=FILDTEOIK2HBORODV&format=json&results=10&artist=radiohead&bucket=song_hotttnesss&sort=song_hotttnesss-desc&bucket=id:rdio-US&bucket=tracks&limit=true http://developer.echonest.com/api/v4/song/search?api_key=FIL...