"In folk the community filters adn creates teh form of the song. In rap the community created the style adn each artist jealously guards his/her own form. "

Sorry Richard, for that sentence, I completely disagree.   The form is out there. There is a competition among rappers, but the same could be said about folk songs. There was a time when everyone had their "party piece" that was shared. That was part of a tradition. Same process, different times, different styles, same folk roots.