By the way, if you want my personal two-penn'orth - tradition has always thrived by absorbing what suited from contemporary material.

When that material actually becomes traditional is far trickier - perhaps when a few alternate versions start to appear, showing the kind of adaptation that happened as a matter of course in oral tradition? But you could stretch that definition to state that Will Young's version of "Light My Fire" demonstrates that song to have become traditional: in the words of Private Eye, "SHURELY SHOME MISHTAKE"?!? How, in the age of recordings, can we distinguish between a commercial cover version and oral transmission at work? It's a tricky one, isn't it?

I'm doing a similar kind of research myself at University of Northumbria, so if you ever feel like just having a good moan about trying to fit reality to theory, etc, feel free to PM me. Doubt if I'll have any answers, but at least a sympathetic ear can help.