Such differences as there are come down to lyrics, style or instrumentation, none of them totemic or particular to folk. You say there are strong differences between the tradition and contemporary music John P, can you point out how exactly?

The differences aren't at all about style or instrumentation. They are about lyrics and melodies. I don't have the learning, inclination, or time to do a thorough analysis of the differences between traditional and non-traditional melodies and lyrics. The best I can offer is an assignment: listen to 100 traditional folk songs. Then listen to 100 contemporary songs. If your ears work the way mine do, the differences (and similarities!) will be extremely obvious in about 95 of each 100. The other 10 songs will be in a gray area somewhere.

After listening to and playing traditional folk music for the last 35 years or so, I can hear a melody and say, "that sounds traditional" or "that sounds modern". When I'm wrong, it's usually because the modern song was written by someone who has been listening to and playing traditional music for most of their life. But then, that's my one quibble with the 1954 definition: there are newly composed songs that, for me, fit in the traditional music genre because they are melodically and lyrically indistinguishable from traditional music. I don't know if these should be considered folk songs or not, and it doesn't really matter much to me.