The InternetDJ API opens this electronic music site to your app. Since 1997 (not a typo!) composers and fans have been able to share and mix music and videos. According to the API's website, requests are limited to 5,000 a day, responses are in JSON and an auth key is required.
With last week's Mashup of the Day winner LastLyrics, you now have your choice of over two dozen web mashups about music that also integrate song lyrics. If you look at this list of song lyrics mashups, you'll see that most of them make use of either one of the 2 lyrics APIs we have listed, one from LyricWiki.org and the other from Lyricsfly.