BEVERLY HILLS, California (Reuters) - Leave it to the prolific filmmaking pair Joel and Ethan Coen to create their own movie conundrum, and engineer (or maybe luck) their way out of it.

For their new film, Inside Llewyn Davis, the brothers Coen painted themselves into this corner: They needed an actor for the title role of a struggling folk singer in the early 1960s who could carry an entire movie, be in every scene, convince the audience he was a musician and play songs live in their entirety multiple times.

"We thought the movie might have been unmakeable," said Joel Coen in a recent interview with his younger brother by his side. "That person just might not exist. Oscar coming in, that was a big thing."

Oscar Isaac, 33, a Guatemala-born, Miami-raised actor and musician trained at the Juilliard School, turned out to be the ticket. Inside Llewyn Davis, from CBS Corp's CBS Films, opens in U.S. theaters on Friday.

Isaac, best known for his supporting role in the 2011 drama Drive, thought he was a long shot for what would be his first lead role, but he nevertheless "obsessed" about learning the folk singing and guitar style of the day, even as weeks went by without word from the Coens after his first audition.

Then there was a stroke of luck before a second audition: He met a guitar player who had played with Dave Van Ronk, the folk singer upon whom Llewyn Davis is based, and who lived above the Gaslight bar in New York's Greenwich Village, featured in the film. He taught him "Travis picking," a widely used pattern in popular music invented by Merle Travis.

Et voila, the Coens found their somewhat obscure actor-musician to anchor their film and around whom they could arrange an ensemble cast populated by big names like Justin Timberlake and Carey Mulligan as a folk-singing duet, and John Goodman as a drug-addled jazz musician.

Award-winning music producer T. Bone Burnett honed Isaac's musical abilities, telling him, "Play it like you play to yourself on your couch." Every song, bar one, was filmed live.

"I felt ready because I wasn't thinking at all what it would look like or what it would be perceived as," Isaac said. "Of course, I could be the one guy to (expletive) up a Coen movie. I definitely knew that was a possibility. But I didn't let myself go there."

AWARDS? 'WE'LL TAKE 'EM'

If the search for Llewyn Davis was unique, so was the premise of the film. Then again, the Coen brothers, makers of the farcical Fargo, the cult favorite The Big Lebowski and best picture Oscar winner No County for Old Men, are not known for bending to convention.

Llewyn Davis is a talented folk singer who toils in the pre-Bob Dylan days of the Greenwich Village music scene, obsessed with being authentic but unable to eke out a living after his musical partner dies. He relies on friends who lend him their couches, but tests their patience with his difficult character.

The Coens said they were fascinated with the memoir written by Van Ronk, The Mayor of MacDougal Street, which chronicled his role in the acoustic folk revival of the late 1950s and early 1960s in the Village. Van Ronk died in 2002.

When the Coens are asked if they just wanted to tell a story about a place and a time that interested them, Ethan, 56, responds with a simple, "Uh huh." He and Joel, 59, are big fans of fellow Minnesotan Dylan and listened to the folk-revival music that influenced Dylan before he lit up the music world.

"You want to tell a story about somebody who is not successful, but very good at what they do," said Joel. "So the story becomes: Why is it that they are not successful? It is a question you want to raise, but not answer."

The Coens' record over three decades, since their debut film, Blood Simple, attests to knowing how to make success out of the obscure, offbeat and quirky premises.

Of their last four films, three have been nominated for best picture Oscars, including the 2010 box-office hit and western remake True Grit and the 2009 dark comedy A Serious Man.

In what may be a harbinger of Oscar nominations to come, Inside Llewyn Davis won the best film honor from the Gotham Independent Awards, sponsored by the Independent Filmmaker Project, in New York on Monday.

Awards, as it happens, matter to the Coens.

"Well you know, we'll take 'em," said Ethan. "They're good. What are they? They help publicize the movie, and that is what they are there for. It is a fine line celebrating versus publicizing. We ignore that line."

As for Isaac, he's happy he's been able to marry the two things he loves "more than anything, which is music and Coen brothers movies."

He says that filmmakers who are just now figuring out his dual acting-musical talent may be "a little too late."

"I am interested in maybe trying some different things, maybe playing a character that is chronically unmusical," Isaac said.

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