"According to MusicHype CEO, Kevin King there are approximately 97 million songs in the world (recorded in the Gracenote* database), and counting (Marsband.com)." 
http://digiev.blogspot.com/2012/10/the-most-popular-downloads-in-sea-of-97.html 


*I don't see any figures actually quoted on their website
http://www.gracenote.com/music/global-music-data/