glueman offered a constructive response, so here's me being civil in return:

(glueman wrote) "I don't believe you can fully understand the motivations and methods of collectors like Sharp and RVW without understanding the milieu that informed them."

I don't think many of us would disagree with that statement, and you would find plenty of supporters for the idea that Sharp was selective in his collecting, or unduly prescriptive in his model for performance. But he published 'Some Conclusions' over a hundred years ago, and things have moved on. I realise that 'The Imagined Village' (which I would guess you're already familiar with) accuses A. L. Lloyd of adopting too many of Sharp's assumptions but, whether you believe that or not, even the 'Second Revival' was fifty years ago, and things have moved on again.

Today's movers and shakers are less likely to be dewy-eyed romantics than hard-nosed commercial interests, and (please acknowledge this, finally) the 1954 definition has precious little influence on what actually gets played now on folk stages here or anywhere else. People who perform traditional song do so because they like the sound of it, or the stories that it tells, and, if they wish to acknowledge their sources, it's out of respect for wonderful traditional singers of the past, not from romanticism or 'noble savage' condescension.

It would be very nice to put 1954 to bed now, but it's worth pointing out that there is an area of agreement between Pip Radish's statement (which I support broadly):

"there probably won't be any more folk music in Britain or Ireland; the conditions under which the process described by Karpeles could work don't obtain any longer."

...and your own: "It offers a closed world to all intents and purposes". (since I wrote that ten minutes ago, I see you're in agreement on that one)

1954 was indeed an attempt to describe a cultural phenomenon which its authors believed was disappearing. Sharp had believed as much in the 1900s and was off the mark only insofar as folksong hung on for longer than he'd expected, either in relatively isolated communties or through the nurturing of individual enthusiasts like Bob Copper and Walter Pardon (whose social group had already given up on it). If you don't accept that it was and is disappearing, then you have to assert that punk rock, or DJ-ing, or karaoke, or the bubble that is the 'folk scene' are the folk music of today and - although there might be a point there in terms of participation - you're still not describing the same process as Sharp.

You might well ask what - if we were to reserve the term 'folk' for 1954-approved songs - we are to call much of the music that is discussed on Mudcat, or played in 'the folk scene'? This breaks both ways, of course: if all of us are 'folksingers', then how do we describe Walter Pardon? If 'folk music' is 'that which is played in folk clubs', then does that mean the vast majority of the world's population have no folk music?

I think we have to accept that 'folk' means different things to different people. To a gathering of folklorists the 1954 definition would be immediately understood. Festival goers will probably accept that anything from Sheila Stewart to the Ukelele Orchestra of Great Britain can be accommodated under that broad umbrella. To the population at large over the age of fifty (who remember the Spinners and the Clancys on TV), 'folk' will forever mean chunky sweaters and hearty choruses. To a pop journalist, anything with an acoustic guitar is 'folk'. To Ritchie Blackmore, in a hilarious interview given about thirty years ago, everything apart from Deep Purple was 'folk music' (i.e. weedy shite). The US Immigration official who interviewed me at Boston in March responded to my self-description as a 'folksinger' by suggesting "like James Blunt, then?", to which I nodded and smiled (best practice with those people).

Personally, I try to use 'traditional' where possible. Or simply, 'old music'.