Anyone got a useful, working definition of what is a "traditional" song?

OK, since Anahata didn't like the last one (which was a definition of 'traditional', not just song) here's another.

It's local music from out there, rooted in a tradition. It is music with a sense of roots, place and community. And it is very much easier to define what it is not. Just climb to the top of a Clapham omnibus and rule out the answers you get from Joe Public to the question 'what is f*lk?'