Richard's mention of Darcy Farrow is, I think, a good example of how a 'modern' song can pass into the 'tradition', albeit my own tradition. I sing it but have never heard a recorded version. It was being sung at Wimborne by two different people and I absorbed the melody over time, liked it so I went and found the words. I added it to my own repertoire although I've never sung it when the people I learned it from are present! I know the story behind it and am aware that there are a hundred or so recorded versions, including John Denver's, but to me it was just another song that I wanted to learn and sing. And I do it differently to the others at Wimborne - one does it as a bluegrass number and the other in a rather 'skiffly' manner.