Once, they were in love

“The Swell Season” basically begins with a haircut. Marketa Irglova is giving Glen Hansard a trim in a hotel room some hours before they’ll take the stage, the distinctive indie rock music they make together providing the soundtrack. It’s an ordinary moment in this extraordinary documentary, so intimate and so natural, you feel as if you’ve stumbled into the room by mistake.

You’ll recognize the couple immediately if you’re one of the many captivated by the film “Once,” the tiny Irish romantic musical drama in which they starred a few years ago. Or maybe you caught them at the 2008 Academy Awards, when they gave a memorable, heartfelt acceptance speech after winning the songwriting Oscar for “Once.” If not, no worries. The opening is intriguing and enigmatic enough to pull you in regardless.

Initially conceived by co-directors Nick August-Perna, Chris Dapkins and Carlo Mirabella-Davis as a more traditional music documentary, “The Swell Season” emerges as an incisive cut at fame’s effect on the real-life music and romance of Hansard and Irglova. It’s an accomplished piece of filmmaking from the trio, who are making their feature-length documentary debut.

The film takes its name from what Hansard and Irglova called their tour when they took the music of “Once” on the road, though that swell season turned into three long years of nearly uncensored access. By the time the film closes with Hansard playing to a packed house at Radio City Music Hall in New York, the directors have managed to capture the growing pains of a band, a creative collaboration and a relationship. Shot in black and white, its cinema verite style feels like an appropriately retro reflection of a group that lived in the indie rock world. Its look is stripped down and simple, the filmmakers nearly invisible -- and that’s increasingly rare (and a nice relief) in this Michael Moore era of documentary-director-as-star.

Hansard and Irglova emerge as very much the same sorts of people they played in “Once.” He’s the fiercely passionate one, she’s more contemplative. He began his career busking on a Dublin street, not unlike his character. She is a Czech immigrant, though not as newly arrived in Ireland as the girl she played. Music brought them together, success broke them apart. On-screen and off , it is a case of life imitating art and art imitating life -- and that is the intersection the filmmakers focus on.

The film was shot on a shoestring: Dapkins handles the camera work, August-Perna the sound and Mirabella-Davis the lighting as they go on the tour with the band with stops at Hansard’s boyhood home in Ireland and the Czech Republic where some of Irglova’s family still lives. There are interviews with musicians and managers involved in Hansard’s career long before “Once,” as the frontman and lead guitarist for the Irish rock band the Frames. And the growing musical influence of Irglova, who was in high school when they first met and only later became his girlfriend.

There are funny moments -- Hansard’s mother fitting a tiny knit cap onto the Oscar; it’s a replica, made by a fan, of the one her son so often wears. There are romantic ones as well, the couple in a moment of naked abandon, running laughing and gasping into the frigid Irish sea during a break in their tour. More moving is the sadness that begins to settle in as Hansard questions whether any of the success matters and Irglova is increasingly frustrated by the blurring lines between fact and their fictional romance in “Once.” You can feel the weariness when Hansard says, “I don’t want to have this conversation again.”

The film is constructed from a lot of free-floating pieces, moments onstage and off, bandmates, friends, family and fans moving in and out of frame, the couple together, then drifting apart. And always the music. Haunting when Hansard and Irglova are collaborating. Raw and filled with pathos when it’s Hansard on his own, or pulling from the Frames songbook. In the end, despite all its disparate parts, the documentary somehow coalesces beautifully into a moving portrait of two musicians who fell in love -- once.

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‘The Swell Season’

MPAA rating: Not rated

Running time: 1 hour, 30 minutes

Playing: At Downtown Independent, Los Angeles