John Renbourn plays on the melody La Rotta and the standard version of John Barleycorn by inserting a complex vocal polyphony.
La Rotta is a medieval dance in ternary meter that was normally performed at the end of a low dance, the melody of this particular route was combined with Tristano’s Lament (14th century) in Jordi Savall‘s video the route begins at 2:00.
The text is roughly the standard one.
https://www.youtube.com/watch?v=B4bsuqas5EI