VIDEO: Oscar Isaac and Jimmy Fallon perform folk version of Katy Perry's 'Roar'

Actor Oscar Isaac is having himself a moment. He's the star of the latest flick from the Coen Bros., Inside Llewyn Davis. The film focuses on Isaac's Davis, a struggling folk musician with some serious talent and an adorable cat. Like many Coen Bros. films before it, Inside Llewyn Davis is driven by the music it contains. As such, Isaac learned how to legitimately play folk songs for the role.

During his recent appearance on Late Night With Jimmy Fallon, Isaac explains to the show's host that, while he played around with bands in high school, he had never really learned the art of folk music until he began preparing for the Llewyn Davis role. Fallon asks him to play a little ditty to show off his skills and Isaac obliges, kicking into a fireside version of Katy Perry's "Roar."

Llewyn Davis, at one point in the movie, says, "If it was never new and it never gets old, then it's a folk song." And I think you'll all agree that you could define this song that way.

Click here to watch the video.