This tune(the one in the Baring-Gould collection, anyway, and recorded by a lot of people) is very unusual in the English tradition in being in a minor key with a variable second.(in Aminor, say, the second note of the scale varies between B and Bflat). An eeire and beautiful effect. There is an English fiddle air called the Northern Lass which deploys this effect also, and these are the only two tunes that do this in our tradition that I've ever heard.