Despite the new (old) setting - the Greenwich Village folk scene of the early '60s - the character Oscar Isaac plays in Inside Llewyn Davis has much in common with many of the sorry souls who populate previous Joel and Ethan Coen affairs.

There are shades of Billy Bob Thornton's barbershop sap from The Man Who Wasn't There, of Michael Stuhlbarg's Job-ian loser in A Serious Man, and of John Turturro's playwright-gone-Hollywood-turned-doomed dreamer in Barton Fink.

"That's what's so great about Joel and Ethan," says Isaac. "Very early on, out of the mouth of Barton Fink, they stated their thesis, which is: 'I want to make theater about the common man.' And that's who all their heroes are. They choose to not make the story about the Beatles, but the guy who opened for the Beatles that night at The Ed Sullivan Show. The one that wasn't touched by fate."

Llewyn Davis, a man with a guitar and a record deal that hasn't earned him squat, is one of those guys. And Isaac, who has been singing and playing music for years, brings him to life with a soulful, if downbeat, brilliance. This is the actor's first "front and center" role, following supporting turns in movies big (Robin Hood, The Bourne Legacy) and not so big (Won't Back Down, 10 Years). Isaac brings it all back home in ways his hard-luck protagonist can only imagine.

"He's a stranger in a strange land," says Isaac, who stopped in Philadelphia last month, happily talking up his character and his film. After winning fans at the Cannes and New York festivals, and rave reviews in limited release, Inside Llewyn Davis finally opens Friday at the Ambler Theater, the Ritz Five, and Carmike at the Ritz Center/NJ. Carey Mulligan, Justin Timberlake, and Coen brothers trouper John Goodman also star.

"Llewyn is like someone passing through, who's looking at it all from the outside in," Isaac says. "He's self-aware to the point of alienation, and that is basically the state of an artist to a certain extent: always observing, always engaging, but, at the same time, observing the engagement. He's scavenging it for later.

"I know there have been moments in my life where I feel a little guilty about experiencing something very dramatic, possibly tragic, but still being the watchful eye, looking for scraps. . . . But that's how I'm wired, that's why I'm doing what I'm doing."

Isaac, who grew up in Miami (his mother is Guatemalan, his father Cuban), has lived in New York since going to study theater at Juilliard (he graduated in 2005). When he read about the Coens' planned project in 2011, he sent in his audition. To be considered, you had to sing and play guitar, and all contenders had to perform "Hang Me, Oh Hang Me," a traditional song made famous (well, famous in folk music circles, anyway) by the late, great, gravel-voiced Dave Van Ronk. Llewyn Davis is modeled, loosely, on Van Ronk and his career - and the Coens cribbed choice bits of their story line from the Van Ronk memoir The Mayor of MacDougal Street.

"They had sent the Van Ronk recording, and I just said to myself, why would I try to do my version of it? Just do this one. So I studied and studied and listened to everything Van Ronk had recorded that I could find, and . . . of course, I mean, I know better than to try to copy his voice, I wasn't going to do that. But to really look at what was behind what he was doing - the phrasing and the mood and the vibe of the whole thing, and importantly, the picking."

The film's casting director forwarded Isaac's video to the Coens. And the brothers summoned him.

"It was a month of agony and waiting," he recalls. "I have lots of friends that have auditioned for Joel and Ethan, and they said it's going to feel like the best audition of your life, and then you just probably won't get it. That was their experience. And sure enough, when I got into the room with them they were the most generous, quick-to-laugh, relaxed people that I had ever auditioned for. And so it felt great, and I had learned a couple of extra songs just in case."

And then Isaac tried to go back to work.

"I kept hearing, 'You're in the mix, man, you're in the mix' . . . and another week would go by, and nothing."

And then finally Isaac's phone rang while he was in a coffee shop on his way to the Manhattan Theatre Club for the opening night of a play he was in, Zoe Kazan's We Live Here.

"I was on my way to opening night and I got the call - what an opening-night gift, right? And it was Joel and he said, 'Oscar, it's Joel. Sorry it's taken a while, you know, we had to go through the process, and there were people to see.' And we talked for a bit - he probably just talked for a few more seconds, but it felt like 45 minutes of him talking to me before he finally told me. . . . And then he finally said, 'But we'd love for you to do it, if you want it.'

"And I said, 'Well, I'll get back to you in a month.'

"Yeah, right. I was dancing in the streets, I was so excited."