Les, you said at the beginning of this thread that some songs because of internal rhyming etc sound as if they come from more of a literate tradition rather than an oral tradition.
A lot of songs that we sing today have gone through many changes because most of them have been passed on to singers who have learned them from the singing of other singers.In doing so a word, line and even a verse will completely change and the more a song is passed on the chances are it will eventually sound like a different song. Even the air will change. I have collected songs for almost thirty years and have changed a few myself. Another reason that songs have internal rhyming and may sound as if they come from a literate tradition could possibly be that we had educated folk back two or three hundred years ago, what of the 'Weaver Poets'
Just a point or two.
cheers eoin