Oops. Missed this one:

I take it from his tone that Sweeney disapproves of the choice of the editors of 'The New Penguin Book' because the material presented fits fairly neatly into the '54' definition and, as I said, includes no "Victorian tear-jerkers, music hall material, 20th century pop songs, snigger-snogwriter compositions" - and no heavy metal.

Though I think I answered it in the first part of my last post. The trouble with the 1954 Definition is that it isn't about one particular genre; all it says, in a nutshell, is that Human beings form communities and in those communities they make music. Big deal, eh? The 1954 Definition tells us nothing about what a Folk Song is that's any different from any other sort of song. And yet we both agree folk songs are different, and we both agree with the editors of TNPBOEFS on their choice of material. I say that difference is one of cultural & social context and idiom - same goes for all the myriad musics on Planet Earth.