Jim,
You tread the verge of the Trad-vs-Modern debate which so bedeviled the Jazz world in the 1950s and 60s. Of course, the answer is that it was both, a core Trad repertoire whose stylistic specificity informed the rest.
Much of what is "Cecil Sharp" folk music is fairly closely datable. Only a fistful of tunes date back more than five hundred years, the wealth of it is really from the eighteenth and nineteenth century. So we know what it is and we know what it is not. But we also know that once it did not exist, and we know that there is a wealth of folk music written since the days of Cecil Sharp. That should be preserved. That's all. Equally, there are repertoires which are almost completely missing from the Archive, particularly from Northumbria and the Border.
Part of the heritage of folk is that there is no "authorised version". Indeed, each performer has to make it their own, in how it works with their voice above all else. Sally Davis may do one thing with the CSH Choir, brushing the boundary of classical music, The Albion Band another (or at least once it reforms), Bella Hardy a third. Our understanding of the music has developed as well, coloured by the growth in Historically Informed Performance in the world of Early Music where the folk world had much of its roots. Our instruments have changed, our voices too. This you know.
I should, however, ask you whether it is actually possible to exclude the edge of Classical music from it. Ralph Vaughan Williams above all else adapted pure folk for the classical world of his time, and we call the CSH Library for him. Sabine Baring Gould turned it into hymns (and some remarkably dirty limericks). Cecil Sharp as well, and Holst. They were in part driven by the market need for accessibility, every bit as much as Bunting was, and indeed we see the same in the Broadside Ballads, Gay and Playford. On the same hand, where does electric folk rock stop, therefore? I think we all know the answers, but I want you to think and find your own. This has all coloured where we are now.
What I'm pointing to is that the Rambling Sid Rumpos of the 1960s, the Trad Jazzers of the Folk World, were all very well but there is more. For example, in the Tapping the Roots gig, Sally's arrangement of Outlandish Knight for the CSH Choir cut the Parrot Coda, initially because of limitations in the ability of the Choir to learn it (the complications of the polyphony meant it had to be done in sections - the Choir has only a few semi-professional singers), then because we realised the point at which we stopped (end of term) made more sense in telling the tale than continuing - which drove me back into the Ballad Books to realise that it comes from another Ballad entirely, Young Hunting, and so wasn't really part of the Ballad. It's the same process Historically Informed Performance engages in. Now, as I mentioned, Martin Carthy was also present, and obviously the Choir's version descended from his. So he had every right to hiss across at the end, "What happened to the parrot?", gesticulating with his hand on his own beak. That put him down as "Trad", with every reason, as he's one of the references. But at the same time the Choir was backing the melody with a line of "sea" sounds in the altos and tenors which was straight out of Debussy's La Mer (I don't know if Sally even realised it) which was on the edge of being acapella beatboxing. That performance has already gone into the new Archive, and so I am suggesting that there is space for more than the most Trad retake of the Archive. How far they want to go, I don't know, but if you don't ask, you won't find out. As I understand it, it's to present a faithful record for posterity of where we are now, warts and all. This is why the original Take Six has been expanded into The Full English, combining texts from the British Library (who the Choir also performs for) and other archives. Exactly the same is happening on an international scale in projects like the Scriptorium, collating the world's collection of manuscripts and incunabile, but that hasn't happened in Folk yet, partly because of funding. Those of you who work in Early Music know how the continental festivals like the Salon de Luthiers at Ars (which may not be happening this year, in passing) is reflecting the same internationalisation of Continental Folk.