McGrath seems to me to be asking exactly theright question .The tune, the harmony, the words, the modes, the appropriate instrument, the economics of performance are things that get concentrated on a lot, because they are measurable and analysable, and of course very interesting. But they are not the essence of the music. That's down to the interaction of performers, creators, dancers and listeners, with people moving freely in and out of those categories simultaneusly,fluidly and continuously. And what they come up with is folkmusic. Sometimes.