As Nick Dow said, at this point, the valuable part of the thread is probably done, but something Lighter wrote might be worth a minor comment: True, but don't we wind up studying the songs we like, based on their subjective appeal? "Trad" or "non-trad" is secondary.

I personally find it a lot more complicated than that. First, the fact that a song became traditional means that somebody liked it enough to remember it. Yes, any particular collection may have become zersungen, and a lot of the tunes have been damaged by being collected from people who could no longer sing any more! And if a song is only collected once or twice, it might be traditional because it appealed to some weirdo. :-) But if a song is widespread in tradition, it's a strong indication that it appealed to people somehow, and that there is probably a good version somewhere, even if the one you're hearing isn't it.

And what is a good song? One that sounds good? It's more than that. To me, the value of a song rises dramatically by reason of being traditional. For reasons I outlined earlier: The traditional songs that go back a long way have historical interest; even the recent ones have psychological interest.

I agree that simply being traditional is not a sufficient reason to sing a song, except perhaps in a very academic context. I very much like the tune I know for "The Wee Cooper of Fife," but I won't sing it because I don't like the words. We already mentioned "Mary Phagan"; I won't sing that because it's a lie. So being a traditional song is not a sufficient reason to sing a song.

But neither is being a "good song" -- or perhaps we should say an "enjoyable song" (something that surely applies to many Beatles songs, e.g.) -- is not a sufficient reason either.

I won't pretend that I have a precise algorithm to determine what songs to sing (although the idea is interesting... :-p ). But being a good song is a necessary but not sufficient condition, and being traditional (my definition of traditional) also comes very close to being a necessary condition for me -- my active repertoire is something like 90% traditional.

Obviously others' mileage varies, or we wouldn't have a songwriting industry!