So, a folk song in Scotland would perhaps include sections on the history of collectors in Scotland, and a century-by-century account drawing on contemporary accounts of practices, and, perhaps, some discussion of the 'Scottish snap' controversy?

There's a web site about Alfred Williams, which mentions Bellowhead, and the first song I found on it, Betsy Baker, seems to have come from a broadside. But this isn't 'in depth' research!