"I don't know how one is to get around the problem of "uninfluenced by popular and art music"."

Indeed. I'm reminded of the song "I'm a Romany Rai", which has been throughly adopted by the traveller community - of course, it started out as a music hall song. What about broadheets? Were they not popular music? They certainly weren't being disseminated orally...

The idea of some pristine community untouched by popular culture is a load of romanticised nonsense, surely.