“I keep calling this a collaboration ‘cos neither of us wants to have a second band,” explains Matt Berninger, referring to El Vy, his project with Brent Knopf, whom he met 10 years ago when The National toured with Portland art rockers Menomena. Down the phone from Los Angeles – where the first gent of melancholy alt.rock is about to have a surfing lesson – he says: “We started out together, playing empty shows and sleeping on floors. We served in the trenches together! I knew he was a prolific writer, so I said, ‘If you have any musical ideas you’re not using, send them to me’. About a month later, he’d emailed over 300 different ones.”

Over the years, Berninger would fill a folder he labelled ‘The Moon’ with the song sketches that would eventually comprise their debut (‘Return To The Moon’, released October 24), keeping the project secret from everyone bar his bandmates and wife. “I didn’t know if anything would come of it,” he admits. Lyrics were written while on tour with The National, on buses, in hotels, on planes and in a tent he pitched in his garden in LA. “My daughter’s six, so the house is constantly filled with activity – it was liberating to realise you can have noise surrounding you and still focus.” On the hip-hop influenced ‘Man To Be’, there’s a moment where he’s interrupted by a cleaner, and the woman’s voice remains on the recording. “I don’t know her name and I never got her to sign a release, but you hear her and me flustered, because I’ve got all the furniture stacked up on the bed and bottles of empty wine.”

Last November, after The National had finished touring their sixth album, 2013’s ‘Trouble Will Find Me’, the pair started “digging into the record”, with Knopf recording his music in Portland and Berninger laying down his vocals at home. He says the songs “needed a different DNA,” to The National and describes ‘Return To The Moon’ as “my most personal record, the most I’ve ever dug into my own past to try and figure out why I’m the way I am.” The album’s lyrics are full of references to his upbringing in Cincinnati, Ohio. “It’s informed by the idea of a young person using music to help them find their way in the world. My adolescence was rocky. It wasn’t because I got into drugs or anything – I was just a dark moody kid, romantically disgruntled and felt like a dork, and using The Smiths and The Cure to find kindred spirits. I was thinking about how I fell in love with music and my cousin Peter telling me how he’d seen The Ramones and The Smiths in [local nightclub] The Jockey Club – to me, Morrissey being in Cincinnati was like spotting a unicorn in your backyard.”

He sees the album as a “almost like a musical” that follows the romance between two characters Michael and Didi, named after Mike Watt and the late D Boon of 1980s punk band Minutemen. “My daughter’s obsessed with Grease and plays the soundtrack constantly. I was thinking of the Minutemen a lot when writing the lyrics, and I think of Didi and Michael as like Danny and Sandy. As a kid, Olivia Newton-John was the first woman I loved – but I liked her plain, singing ‘Hopelessly Devoted To You’ rather than the curly-haired leather one at the end.”

El Vy will tour throughout this year – visiting London, Manchester and Dublin in December – working around the schedule of The National, who are currently writing their seventh album. “We did a camp out retreat in New York a couple of months ago, and we’re having another one in LA in a few weeks. We have 30 sketches of songs so far.” The band’s Aaron Dessner has been temprarily naming the nascent tracks after towns in upstate New York. “Before, he’s named them after things like civil wars. All the songs that turned into ‘Trouble Will Find Me’ were named after children of our friends.”

Berninger says outside collaborations are integral to ensuring The National “stays healthy”. “I think the band were initially nervous because if I made a bad record, it would reflect badly on us. But fortunately they love ‘Return To The Moon’.” From what we’ve heard of the record so far, they certainly won’t be the only ones.