There are numerous versions and variants of "John Barleycorn", a song I grew up with, but the version I sing is taken from a popular German songbook. I used to find it pretty boring until I started playing the English concertina. The tutor I used was Roger Watson's
Handbook for English Concertina
and in it he goes into a detailed technical discussion on minor keys and transposed Dorian modes using "John Barleycorn" as an example. This woke me up to the fact there was much more to such "simple" folk-music than meets the eye.
The song itself deals with the magical transformation of impotent barley seed into a substance powerful enough to strike the strongest man down. A sort of Charles Atlas story.