It’s a rainy Tuesday afternoon in March, and Matt Berninger and Aaron Dessner of The National are seated in the suite of a West End hotel. Mere days have passed since High Violet, their fifth studio record, was completed, mixed and mastered. A Dylan-esque perpetual tour fills their calendar for the year, with headline appearances at summer festivals and worldwide gigs until December. Approaching the end of an arduous day of interviews, a massage has been booked at the spa round the corridor to rid them of any weariness. But somehow, the pair remains enthusiastic, even infectiously so, as they discuss the new record with exuberance.

"We wanted it to sound like hot molten tar," says Berninger, singer of the New York-based band, "whatever that sounds like". Released last month to universal acclaim, High Violet is the sound of a victory lap of a band whose success has been the result of a subtle, decade-long crescendo into the consciousness of record-buyers.

Forming in 1999, the quintet comprising Berninger and two sets of brothers quit their day jobs around the release of Alligator, their 2005 breakthrough. Boxer, released two years later, cemented their reputation as frontrunners of the American Indie scene. Its slow-burning appeal inspiried a loyal fanbase and ‘Fake Empire’ was hand-picked by the Obama Campaign. "We are very happy with the record," beams Berninger. "We were able to do a lot of things with it that we hadn’t planned to." Despite road-testing material across recent tours, Dessner (multi-instrumentalist and the band’s musical mastermind along with his brother, Bryce) is adamant that their latest offering is the product of hours of grafting in their Brooklyn studio. "It’s really hard to have any perspective on songs when you’re playing them live", he says. "Finding the right tone, the subtleties and the nuances of a recording is like finding a needle in a haystack, and it takes a long time. The songs we learn to play live almost become too big and too muscular."

In person, Matt and Aaron are fixated with attempting to express these delicate subtleties that form a sound equally as brittle as it is brash, and as uplifting as it is devastating. Album opener ‘Terrible Love’, for all its boisterousness, retains fragility, boasting a nervous energy which persistently teeters on the brink of self-imploding chaos. Dessner describes a process of "catching that adolescent version the song, where it’s not completely grown up". Rigorous thoughts like these govern The National’s creativity.

Renowned for his pathos-ridden lyrics of anguish, turmoil and despair, sung in a distinct baritone, Berninger makes for a mesmerising, albeit downbeat, frontman. One brief glance at the album’s tracklist reveals titles like ‘Afraid of Everyone’ and ‘Sorrow’. "Fear and anxiety," he says, are "things we’ve always channelled into our songs from the very beginning". His expression of this personal melancholy imbues his songs with their tension, and the lucidity with which he discusses his poetry would, no doubt, impress in a Cambridge supervision. "There’s a reason why water’s a clichéd metaphor" he declares. "If you look up [its] abstract meanings, you will find almost everything. People use it to describe life, death, they use it as a metaphor for travel or loneliness. On this record, I use rivers, oceans, rain, lakes..." he lists. "I also use birds, and furniture, and cake. I’ll use cake for ten different reasons, meaning different things every time."

New York, the Ohio-born band’s adopted home, also occupies an important space in their music. Manhattan’s legendary venue, Radio City Music Hall is submerged by a flood in ‘Little Faith’, a standout track, with a refrain of "Stuck in New York / And the rain’s coming down." It is one of many instances on High Violet, where the Big Apple is depicted in a seemingly derogatory light. "I love New York", insists Berninger. "Not to mention [leaving] New York would be like trying to write love songs while not think[ing] of the person you actually love. But on this record there was a need for more space." The sense of claustrophobia, he explains, arises from the small apartment he occupies with his wife and newborn child. The need for "wide open space" is most prominent on ‘Bloodbuzz Ohio’, a song about "leaving New York and trying to reconnect with the past. The ocean," he gestures, "that feeling of having your body on the waves, is like a wide, open panorama, as opposed to the cramped feeling of New York and the valleys of the dead."

Listen carefully behind the quivering guitars on ‘Afraid of Everyone’ and you’ll hear a shrill falsetto. That’s Sufjan Stevens. One of the many guest stars on the album including Justin Vernon of Bon Iver and Richard Reed Parry from The Arcade Fire, they are just three of the artists also to be involved in Dark Was The Night, a charity LP released last year, conspired by the Dessner brothers. Widely regarded as a contemporary ‘Who’s Who’ of American indie, the triple disc extravaganza is the product of three years of haranguing acts for songs and features contributions from David Byrne & Dirty Projectors, Yeasayer, and Feist. "There was never any discussion of what is the indie scene today", recalls Dessner. "Everyone we asked were people whose music we respected. It’s a mix of covers and originals, with no real style or theme. The one cohesive thread is that we asked people with an attention to craft and detail, [those] who self-produce and make their own records." On course to raising a million dollars for Red Hot, an AIDS organisation, the project has been a overwhelming commercial and artistic triumph.

The zeal with which The National approach every aspect of their music translates into an emotionally-intense live show. At their sell-out Royal Albert Hall gig in May, for instance, Berninger finished up amongst the crowd, as he scaled the stalls of the historic venue. The intensity of performing songs so laden with pathos has its demands, and Berninger acknowledges this himself. "It is hard to do shows late at night", he agrees. "The pathos in our songs is a natural by-product of standing on stage under lights with people watching. It’s a scary intense environment and it’s hard for everybody. We do lose our minds a little bit after a while." The process of touring proves so draining, songwriting on the road is impossible, and even pre-show sightseeing is ambitious. "I can almost never go to after-parties", Berninger confesses.

"Not without a body guard", Dessner interjects.

"Or without a bag over my head", laughs Berninger.

"Usually I’m a little bit drunk and at my wits end, so socialising doesn’t work so well. It’s an awesome, amazing feeling, as it’s unbelievably satisfying and cathartic…but [afterwards] I can’t do much else."