Rap is surely a great deal more "folk" than the tricksy educated musicians attempts to rearrange folk tunes for the concert-goers ears, over the last century or so.
The origins of rap and hip-hop can be easily and directly traced to the Bahaman traditions of maritime music(and many other similar related traditions). The blend of fast witty sarcastic rhythmic talking with powerful dance rhythms and slow melodic lines is a well established area of Afro-Caribbean culture, with deep folk roots going back a long long time. A basic background would be easily acquired by listening to the CD "Rhyming Singers of the Bahamas" for example, or many other Caribbean field recordings. I am exploring these historical connections (between dance tunes, sea song and witty rapping) in ongoing projects in Liverpool at this moment. At the very least, it is adding the distinctive "voice" of urban youth to the folk scene: which is, let's face it, becoming increasingly dominated by a very educated and university-based middle-class aproach.