This question was answered on an interview with The Sentimentalist:

Alison: A guy ? [laughs] You’re talking about that realty low voice ? That’s me. I can go very low [laughs].

Sentimentalist: Okay. I was thinking that it couldn’t be a man. I didn’t think you’d bring someone like that in [laughs].

Alison: But when we do it live, the two guys that play violin and keyboards are going to be helping me out on that. It’s always really difficult singing such a low vocal live, because you’ve got very little strength there to project. The men will come in handy on that one [laughs].