If all music is folk music then the question of whether rap is folk has no meaning. The proposition would certainly surprise most of the denizens of Leo's Red Lion, where there is today a "Battle of the bands" for the opportunity to play a support slot at Bloodstock, and I would be surprised if they took kindly to being told that thier music was folk music.

The expression "folk music" was used with some if not perfect consistency from teh mid 1800s to the mid 1900s. There is a difference in kind, not a difference in style (although there may also be differences in style) nor a difference in quality. To say that the cocept of folk music, like the concept of the noble savage, is a pretension and a condescension does not answer the question of whether the distinction between songs shaped by the community (which is not the same thing as song styles shaped by the community) and songs shaped only by specified creators and/or economic influences is a valid one or not.

It was generally assumed until Lloyd that only agrarian or peasant communities created folk music and song. Lloyd's assumption and assertion that there might be industrial folk song was handicapped by dearth of examples (as discussed on this forum). Both models involve the predicate that there are songs that by evolution are extant in a community so that the current form(s) in the community cannot be shown to be the work of known authors (and I suggest that nowadays that might be despite the known identity of the originating author, so long at the song is no longer principally as he delivered it. It is a "top down"/"bottom up" difference and I have never yet seen any denial of the distinction of type that is in the least credible.

What the correct definition is may be open to some discussion (and I adhere to one view as for example WLD does to another) but to say that there is no distinction seems to me to be unlikely to be justificable. SOme may say that it is a distinction without a difference, but that, too, cannot be so while different societies have different common forms of music.