If / when arrived at, how would you render such an understanding readily comprehensible to someone completely new to the area, who might lack knowledge of your points of reference?

I think it's already been arrived at, CS - we have a vast body of collected material we might think of as English Language Traditional Song which can be discussed as much in terms of its structure, modality & lyrical imagery as its (possible) derivation, distribution and diversification - whatever sort of life it once enjoyed in its natural habitat as it were. The evidence is impressive, but I think the definitions we're dealing with don't really go deep enough into the creative nature of the beast itself. Like Popular Music today songs were created by individuals steeped in a tradition of creative song making within a genre of Popular Music, however so derived. Unlike Popular Music today, the names of these song makers haven't come down to us; even on the Broadsheets we don't find claims of authorship. Now, whether the broadsheets represent an initial source or a medial literary stage has been debated at length before, but whatever the case, in an oral / aural culture (in which to hear a song casually you generally had to sing it yourself) songs will evolve as they get passed on from one singer to another, especially given the creative nature of singers.

There's plenty of evidence to suggest that certain singers didn't sing the same song the same way twice (i.e. Mrs Pearl Brewer of Arkensas, who gives two notably different versions of Child #20 collected within months of each other) which is a further indication of a creative & improvisatory fluidity which, whilst being anathema to Folk Music today, seems to have been the very benchmark of Traditional Song in its natural habitat. This is in the very nature of oral / aural folklore, where the empirical essence of such lore lives and breathes in such a way that its collection and preservation, in effect, kills it stone dead like a pinned butterfly or a piece of choice taxidermy. What we are left with are specific instances, snap shots, shards and fragments upon which the various theories and definitions have been postulated, as romantically as scientifically, and at some considerable remove from the actual context of the thing. In folkloric study context is all, but the context is the very thing we don't have. Besides which, in too many cases the evidences have been falsified and tampered with by people who should have known better, standard works received in good faith by generations of Enthusiasts of Traditional Song have been shown to be as fraudulent as the Piltdown Man, leaving us a little wary of the whole thing as a result.

The creative & idiosyncratic genius of the Traditional Singers themselves is something worth looking into. Too often I fear material has been seized upon as being Traditional which should be seen as the creative property of the individual singer. Davie Stewart, for example, was recorded on various occasions remaking McGintie's Meal an' Ale (a song with a known author I might add) afresh, in much the same way that John Coltrane remade My Favourite Things afresh each time he played it. This fluidity stands in stark contrast to the way things are done by revival singers, and not without good reason. In its natural state I would argue Traditional Song was as fluid as jazz; I have even heard it suggested especially gifted singers might extemporize entire songs on the spot - freestyle folk song! Why should this surprise us? We find it in vernacular traditions the world over, from Serbian bards to Rap artists, and certain songs in the English Speaking Tradition would demand a spontaneous verse or two - and I dare say we all know of gifted individuals who can come up with such things today.

What of the song makers themselves? One might think of Tommy Armstrong (1848-1920) as case in point; his masterful compositions are evidently of a tradition, in terms of structure, narrative, imagery and language; he frequently uses Traditional melodies and they remain a cherish window into the long vanished world of the Durham Coalfield. They are the work of one eccentric idiosyncratic genius yet bare testimony to the vast tradition of popular vernacular song he was but a part of. Do we think of them as Traditional Songs? I know I do, but then again I always point to the aims of the International Council for Traditional Music (formerly the International Folk Music Council who gave us the 1954 Definition in the first place) which are: to further the study, practice, documentation, preservation and dissemination of traditional music, including folk, popular, classical and urban music, and dance of all countries. In this sense the very phrase Traditional Music is tautologous - the very nature of music is traditional and I can't think of a single music that can't be defined as folk according to the 1954 Definition simply because the folkloric remits of 1954 are very different to those of today. Popular Music continues, thrives, evolves, changes, on just about every level imaginable, yet this isn't what we mean when we say Traditional Song because here we're using Traditional largely as a noun. In it's adjective sense it becomes a whole lot wider - certainly too wide for Mudcat, or the EFDSS, or the folk scene as a whole. Certainly too wide for a proposed Mudcat Definition which can only point to the body of collected material be it in the Grieg-Duncan Collection or the Max Hunter Collection (etc.) and say those are Traditional Songs. Maybe a good place to start would be sorting out the mess in the DigiTrad, so we might have something worth pointing at around here too??