OK, it's not what you're thinking.

Calendar Girl is a singer who decided to write a song every month. She posts her song in a simple format of vocal + simple keyboard backing, and also the vocal and keyboard tracks separately. Anyone is then welcome to download the tracks and make their own version of her song with them. In a way it is the reverse of a backing track; you start with the vocals and build a backing track to it.

This website was apparently started at the beginning of the year. I just stumbled upon it 3 days ago. I listened to some of her original tracks, then listen to some of the songs various people build from her tracks and I'm amazed at how the whole song is essentially re-imagined. Since I try to write music, this is fascinating to me. This kind of music may not appeal to you, and be forewarned that the pages for each month takes a long time to load because apparently all the songs are downloaded for each of the month pages.

In case you are interested, the link is:
http://www.calendarsongs.com/Calendar%20Songs.html