For a kick, research the 1964 Newport Folk Festival and think about all the versions of folk on display: A Mighty Wind-type balladeers, grizzled bluesmen, Lower East Side speed-freaks, Dylan debuting his psychedelic "Tambourine Man." People worried about What Folk Meant. They went to the New York Folklore Society and debated it. Nobody ever sorted matters. Or for the really long version, see Bernard Gendron's Between Montmartre and the Mudd Club: Popular Music and the Avant-Garde. Gradually, Gendron argues, the two categories have thoroughly blurred.