"Byegone" is two things: a soused conversation between a pair of friends or lovers, and evidence of the tight bond between the songwriter Justin Vernon (Bon Iver) and the cerebral band Collections of Colonies of Bees--a collaboration known as Volcano Choir. The song plays like a short film that says a lot in just a little time about companionship, overcoming fear, and, well, being from the North. (Vernon consistently uses Wisconsin as a supporting character in his work.) Though "Byegone" is one of the more distinctly rock songs Volcano Choir has released, it sacrifices none of the imagination present throughout most of Unmap, the six-piece's 2009 debut. The shift toward a more coherent lyrical narrative and a tidier, more structured sound works for them. "Byegone" is the first single from Repave, which arrives September 3.