I actually have this idea about Music social network and not really just for music but that is major part of it.. I think there is if you approach it the right way
I think myspace is a good social media for music because here you can listen music of their who are following by you.
there is not really a big market for a music social network because of all the other sites which are free to add music too like soundclick and sites like that
Agreed, myspace and youtube are those sites that is considered as good Music social networking sites..most musicians and their followers are into it