IN 2011, Dustin O'Halloran and Adam Wiltzie released their first album as A Winged Victory for the Sullen. The duo's beautiful self-titled debut delicately brought together O'Halloran's modernist piano and Wiltzie's textured guitarscapes, honed during his time in the influential drone band Stars of the Lid. A Winged Victory for the Sullen was well received by critics, a hushed announcement of a promising new force in the world of ambient, neo-classical music. It took O'Halloran and Wiltzie two years to make—time well spent.

They were working on new Winged Victory material in 2013 when they were approached by choreographer Wayne McGregor, artistic director of London contemporary dance company Random Dance, about composing music for his new production, Atomos. Once O'Halloran and Wiltzie got a sense of the project, they decided to drop what they were doing and join the effort.

"It just seemed to make sense to start fresh," O'Halloran says from his home in Berlin. "Wayne gave us a lot of nice inspiration and it just felt like we could try to do it all with a blank slate."

There was one trick: The duo had to create more than an hour of music in about four months, an all-out sprint compared to the pace they'd taken with their debut record. The timeline was "terrifying," Wiltzie says from a forest outside his hometown of Brussels.

"I'd never had to work that quick before," Wiltzie says, "but it did open us up to a new way of collaborating together, to just sort of let go of your ego a bit more, and just let go and move on, because you don't have time to be precious about anything."

O'Halloran and Wiltzie finished the task—barely. They were writing the last bits of music just days before they performed it at the London premiere of Atomos in October 2013. The quick turnaround, the desire to please McGregor, and the production's many moving parts added up to a nerve-racking experience, according to O'Halloran.

"The dance piece, everything was so perfectly timed. There are lights. My computer had crashed a week before the show," he says. "We were just praying that... we didn't mess it up."

They didn't, but A Winged Victory for the Sullen have also become much more comfortable with the material since, playing it live without the dancers many times. They released the music as an album, Atomos, through Kranky Records and Erased Tapes in October. Even without the accompanying choreography, it's an engrossing piece of art: elegant, deliberate, dynamic, and imbued with its own kinetic personality. It also expands on the debut's ambient chamber music, augmenting it with synthesizers and other electronic sounds.

Wiltzie says he and O'Halloran didn't know they had composed Winged Victory's sophomore effort until they were performing with McGregor's dancers. Leading up to the performance, there was simply no time for that kind of thinking.

"It's not just about me and Dustin, it's a whole other entity. A sentient being is involved. So it becomes a completely different thing," Wiltzie says. "[Wayne] came to us. It was his idea. This music never would've happened if we hadn't met this guy, so when you're in this hole, this four months, just trying to reach the end, the last thing on your mind is, 'Are we gonna release a record?' You just want to make something. You just want to finish the challenge."

He continues, "It wasn't until we premiered that we realized, 'Hey, this sounds like a record. Maybe it could stand on its own.' And it's been a real pleasure to play the thing."