The whole subject of chords to folk tunes is controversial. I've heard heated discussions about guitarists playing the wrong chords or "trying to be too fancy" when accompanying sessions, with the more traditional players insisting that many tunes have really obvious simple chords which shouldn't be strayed from. And while it's true that folk melodies can be harmonized in wildly different ways (just listen to Andy Irvine's crazy chords in his version of Captain Thunderbolt ), there does seem to emerge a "consensus" for some songs, and certain melody fragments overwhelmingly suggest certain chords over others.