When I first encountered a post by Sir John Barleycorn's, I wondered if he was referencing Jack London's book (which I read circa 1977).
Actually it is in reference to the old English folk song. Back in his book learnin' days, SirJohn helped cover tuition by tending bar.
You can hear a MIDI version of the old English folk song on the web. Go to http://www.contemplator.com/folk.html#top, go to songs sorted by country, go to England, go to John Barleycorn.