Fredrick Douglass described something very similar to rap performed by slaves on the plantations where he lived. I believe rap has it's roots in African tradition, and was born of a traditional folk art.

This having been said, I would like to track down the next idiot who drives past my apartment in the wee hours of the morning, playing rap at top volume, find out when he sleeps, and drive past HIS residence playing some of my favorite bagpipe music at top volume.