There's no telling when a concert by the Haden Triplets might break out.
On a recent afternoon, the sisters who make up this L.A.-based group — Tanya, Rachel and Petra Haden — were gathered in a Burbank dressing room before an appearance on Conan O'Brien's show. A conversation about the type of old-fashioned folk songs the triplets sing on their self-titled debut album turned to "You Are My Sunshine," which Tanya pointed out is much darker than many people realize.
"The singer goes to sleep and dreams that her significant other is alive again," she explained. "Then she wakes up and is, like, 'Oh, I was only dreaming. He's still dead.'"
Considering the grim sentiment, Petra said she was surprised the composers hadn't written the song in a moodier minor key. And at that the 42-year-old women broke into a demonstration of how that might sound, their voices blending instantly in precise three-part harmony.
Impressive? Very. But the impromptu performance was just family business as usual.
The daughters of the celebrated jazz bassist Charlie Haden (who died last month at age 76) have been singing together since they were young, an extension of a family tradition that stretches back to Charlie's childhood in the Midwest, where he performed in a traveling country group with his parents.
Growing up in Los Angeles, the women moved away from roots music. Rachel and Petra formed the precocious pop-punk band That Dog, and Tanya later played cello with Silversun Pickups.
"When you're a kid, you rebel," Tanya said.
Yet the vintage sounds their father had introduced them to, along with the bone-deep experience of singing harmony, remained in the sisters' blood, as Rachel described it. So two years ago they took up with Ry Cooder, the veteran guitarist and producer known for his work with Neil Young and Randy Newman (among many others), and began working on an album of traditional folk and country songs. Their selections included stark but crafty tunes like the Louvin Brothers' "When I Stop Dreaming," Bill Monroe's "Memories of Mother and Dad" and the Carter Family standard "Single Girl, Married Girl," which the women sang on their father's 2008 album "Rambling Boy."
"The Haden Triplets" came out in February on Jack White's Third Man Records, and the trio is scheduled to play a free concert Thursday night at the Skirball Cultural Center.
"Their singing, it's so stirring," said Cooder. The producer remembered hearing the sisters for the first time after his son Joachim (who plays drums on "The Haden Triplets") invited him to check out the group's performance at a benefit honoring Charlie Haden in 2012. "And as soon as they hit a chord, well, I didn't think in my lifetime I would ever hear that."
Cooder said the Hadens summon the "shared cellular whatever-the-heck-it-is" that once distinguished singing by the Louvin Brothers, the Stanley Brothers and the Everly Brothers.
"That sound is gone, really," he said. "So I thought I'd never get the opportunity to do anything with it. But then to hear them — I said, I have to do this. I asked for their numbers and called them the next day."
The group rehearsed and recorded in a house in Los Feliz that Tanya and her husband, the actor Jack Black, owned but hadn't yet moved into with their two young children. Cooder loved the acoustics of the empty rooms, though the unconventional environment presented some challenges.
"The house had 1915 electricity, so we had to bring in generators," he recalled. "And we paid the neighboring gardeners to shut off the leaf blowers every time we were ready to record: 'Here's 20 bucks. Come back later.'" Yet the playback, he said, was "astounding."
"This isn't an act for them," said Cooder, who acknowledged that this sort of rustic Americana has come back into vogue lately thanks to bands like Mumford & Sons and the Lumineers. "It's not something to wear. It's just instinct."
Indeed, the sisters make no attempt to embody the old-timey characters depicted in the songs they perform. During a talk at her house, Tanya happily admitted to wondering about the rumors regarding a more modern Carter family: Jay Z and Beyoncé. (Her children's nanny had attended the couple's Rose Bowl concert the night before.) And as with any other denizen of the social-media age, the women's smartphones beeped regularly with incoming messages.
It was Facebook, in fact, that provided what might be the impetus for a second Haden Triplets album.
Not long after Charlie's death, a cousin of the sisters' in Missouri — someone they said they haven't seen since they were 10 — sent them a message with photos of a trove of books he'd discovered, including a Haden family songbook.
"He was like, 'Look what I found!'" Tanya said. "So I showed them to Ry, and he said, 'That's your next record.'"