But why should you want to??

Part of the beauty of Folk Song is that whatever structure you attempt to ascribe to it you'll so often find that it's the exceptions to the rule which give the thing its beauty . .

Or as Martin Simpson was sometimes heard to say, when introducing Betsy the Serving Maid "If anyone wants to work out what time signature this is in - good luck!" (And that was when he sang it slowly . . .)

G.