but I can still think of a shedload of music that doesn't fit into these descriptions

I'd be interested in hearing what they are, Steve. I would also question that any human community could be considered unsophisticated, though obviously this was a requisite for genuine folklore by the early collectors, certainly up until 1954 anyway. It smacks of colonial paternalism, however so well-intentioned in its sentiment, much as Kipling gave evidence to in The Land which celebrates the God given functional status of 'the rich man in his castle, the poor man at his gate' which was later anathema to the Folk Scene as a whole despite (or maybe because of) its pedominately middle-class demographic. Even now its rare to meet a right-wing folkie (I know a couple, both of them working-class) despite the fact of the entire rivival being predicated on class condescension.