ProgrammableWeb lists many popular Music APIs in the directory including Last.fm, 7digital and Spotify Metadata. This post features a few really creative, entertaining mashups that use a few popular Music APIs.
Ivy FM uses Last.fm and YouTube to create a mashup that allows users to continuously play music by choosing a genre based channel such as alternative, blues, hard rock and pop. The site also displays related YouTube videos and offers the ability to search by music group or a specific artist.
MusicWall is a mashup that lets you discover new music. Once an artist or music group is provided in the search box, a list of music videos is displayed. When you select and play a video from the list, options to search for related artists and similar tracks are shown underneath the video playing in the right column. This mashup uses Last.fm, Spotify Metadata and YouTube.
Music Pop Quiz is a mashup that uses 7digital to create a fun music based quiz game. You can select favorite genre to play in such as hard rock and metal, pop, jazz and alternative and indie. The questions are randomly generated and they become more difficult with each level.