I play bass and it's mostly metal stuff. I kinda want to larn a new style of music that will diversify my playing. I have been looking at classical stuff like http://www.youtube.com/watch?v=UrAkCqgJeYg and find it fascinating. I'm jsut wondering how would I write stuff like that. Is there a theory site that will help me compose stuff like this or what? I'm open to most any genre and am open to any reccomendations.

Basically, I just want a new style to play and maybe a siet to help me guide myself through it.