And he's played guitar (at Juilliard), a skill that helped land him the lead in "Llewyn," the Coen brothers' melancholy comedy about a gifted folksinger (songs curated by T Bone Burnett) on the cusp of either stardom or something less, a place that Isaac himself knows well.
"That's what this movie is about. I mean, it's about so many things. But things have to go right for you to quote/unquote 'make it.' More often than not, they don't. I think the Coens feel that things could just as easily have gone the other way for them. I know that things could have easily gone the other way for me."
He's hardly been starving. He was Prince John in "Robin Hood," Joseph in "The Nativity Story." He's had roles in "Sucker Punch," and "Drive." But he's most famous in the business for the role he lost - to Jeremy Renner as the sub for Matt Damon in "The Bourne Legacy."
That's the way things go in Hollywood. And that's the way things might have gone for Isaac in his "Llewyn Davis" audition. He knew the movie was about roots music, so he prepped by listening to guys like Mississippi John Hurt, and let it all hang out when he sang for the Coens.
"I was looking everywhere for what song to play at the audition. So I'm doing 'Candyman' and these big blues numbers, and really sweating and pouring it all out. And the Coens are like, no, we're thinking more white. Like English and Scottish folk music. And that's not my bag at all."
Isaac couldn't have known it at the time, but one of the things he's required to do as Davis is to choose the wrong song for a crucial audition. It may be the Coens saw something in his confusion that helped him win the role.
In any event, the Coens liked what they heard. They gave Isaac a song to study and play.
"So they brought me 'Queen Jane,' and I said, 'Really?' And they said, 'Yeah, it'd be good if you did this.' So I spent the next month trying to find some way into this song about a medieval C-section gone wrong, and it just didn't make sense to me. T Bone and I worked on different arrangements and figured it out, musically, but it wasn't till afterward, when I watched the movie, that it finally sunk in. Geez, of course it's this song."
Spoilers will be preserved, but the movie is arranged ingeniously - songs like "The Death of Queen Jane" embellish details of story and character in surprising, sometimes retroactive ways.
"The movie for me was an experiment in context. I don't get a moment in the movie to express who Llewyn is. I don't externalize. I just have to think it and feel it and have the faith that the Coens will add the context."
His character is based loosely on a pre-Dylan folk artist named Dave Van Ronk, but Llewyn functions in the movie as an avatar of every artist who almost made it.
Isaac said everyone involved - even the celebrated Coens and Burnett - felt an affinity for Llewyn, who makes interesting artistic choices but almost always the wrong commercial choice.
When the Coens look at Llewyn, Isaac said, they're sort of wondering what might have been.
"I think the movie says something about the squareness of career calculation. That it never really leads to anything lasting or anything that really contributes to the medium. And the impression that I get working with the Coens is that a lot of their choices are coming from instinct. I think they're guided by their own taste and intuition, and they've been really fortunate. I think they are geniuses, but I think they are lucky geniuses."