I'm learning how to play blues right now using the excellent Blues lessons with Anders. But i feel like I'm missing something. I know a bit of music theory, but what I want to be able to do is take a song like "Jingle bells" in C, and turn it into a blue song. I just dont know how to do this. Is there a good section on this site for music theory?

I want to be able to write my own songs, is there a good song writer section?