Though they’re not a couple, there’s a heavy tension emanating from the Civil Wars’ Joy Williams and John Paul White that’s palpable in the music. Opening with the title-track to their Poison & Wine EP, the duo gives us the romance we wanted but never got from Markéta Irglová and Glen Hansard’s performance in the 2006 film Once. Listen to their voices braid together on the following “Go” where Williams’ breathy inflections resonate with White’s high tenor. His voice is able seep around hers with such a tight embrace that a third overtone can be heard vining out of the mix. The similarly bewitching “Pressing Flowers” starts with White whisper-singing for Williams before branching out into another stunning example of the their folk-based repartee.