Andy's post reminds me of an incident at a singers club many years ago now. A former resident was back in the area visiting family and performed her "party piece".

Once of the current residents, who hadn't known her before she moved away, also had the song in her repertoire. She had been to the bar and was standing outside the room incandessant about "her" song being sung.

Actually both parrotted the same version by Martin Carthy note for note.