Digital Spy sat down with Isaac and Carey Mulligan, who co-stars as a fellow singer with whom Llewyn shares a complicated past, to discuss how they developed their characters with the Coens.
"I thought a lot about the comedy of resilience, and why that's funny," Isaac explained of Llewyn. "I thought of people like Buster Keaton who always has this impassive face, this slightly melancholic face, even though all this crazy stuff is happening around him.
"In our version, instead of buildings falling down or near-death experiences, it's the music. That's the major feat, and that's your key into him."
Isaac and Mulligan also discussed the cathartic tone of the songs in the film, which were performed by the cast and produced by T-Bone Burnett and Marcus Mumford, and the Coens' deceptively "casual" approach to filmmaking.
Inside Llewyn Davis will be released in the UK on January 24. Watch a clip below: