The Georgia Straight’s conversation with Martha Wainwright has just come to an abrupt halt, but we can hardly blame the Montreal-raised, New York–based singer-songwriter for that. After all, we’d already determined that family comes first.

The context is a discussion of future prospects for the Wainwright Sisters, Martha’s new collaboration with half sibling Lucy Wainwright Roche. Songs in the Dark, the duo’s first release, is a lovely extension of both the McGarrigle Sisters, featuring Martha’s late mother, Kate, and the Roches, which contained Lucy’s mom, Suzzy Roche. It’s only natural to hope for more, and Wainwright suggests that might be possible.

“Well, God knows there’s so much material, potentially, for this kind of a thing,” she says, reached at her NYC home. “I think it’s the beginning of at least a singing relationship with my sister, which didn’t exist before, and that’s fabulously exciting.”

Then she turns away from the phone to ask, with a mixture of affection and exasperation, “Okay, what’s going on here?

“My son just ran up the stairs naked,” she explains, which seems a natural cue for us to make our goodbyes. Family does come first.

It’s fitting, then, that there’s more to the team that made Songs in the Dark than just the two half sisters. Wainwright’s husband, Brad Albetta, recorded the two singers in a rustic cabin that their grandfather, Frank McGarrigle, built when his own daughters were small. Aunts Anna and Jane McGarrigle contribute their voices, as do cousins Lily and Sylvan Lanken. And the Songs in the Dark repertoire extends from Depression-era standards like Jimmie Rodgers’s “Prairie Lullaby” to items from the sisters’ father, Loudon Wainwright III, and family friend Richard Thompson.

Linking all 16 songs is an undercurrent of darkness—and when we ask why, Wainwright has a ready answer.

“I had the same question, and a couple of answers came up that I felt were kind of amazing,” she says. “One was that lullabies were used not only to soothe children, but also to warn them of the difficulties of life. Fifty years ago, or 100 years ago and before that, children were probably much more surrounded by death.…There would have been wakes where you’d have open caskets in your house; there was just a lot more exposure to morbidity. So there’s a theory that lullabies were there sort of to prepare children, psychologically, for these realities.

“And then the other theory, or one of the other things that seemed interesting to me, was that oftentimes women would sing to their children because children were the only people there to listen to them,” she continues. “They would bare their breast, and their pain, if their husband was off at sea, or down at the pub, or had run off with somebody else so that there was no money or food in the cupboard. These melodies were perhaps sweet, but they also allowed these women to express some of their pain and their sadness to somebody who would listen.”

You don’t need to be heartbroken, abandoned, or even a parent to enjoy Songs in the Dark, however. All that’s necessary is an appreciation for the kind of harmonies only siblings can provide.

The Wainwright Sisters play the Vancouver Folk Music Festival’s Stage 2 and Stage 5 on both Saturday and Sunday (July 17 and 18).