Joel and Ethan Coen’s Inside Llewyn Davis (Rated R) is a downer – a rich, glorious downer, dripping with authenticity and boasting a killer soundtrack. It’s a hardscrabble story of a folk singer whose best days are behind him (and those days weren’t that great to begin with), and a make-or-break week that could change everything … or not. It’s 1961, and Llewyn (Oscar Isaac, the doomed ex-con husband in Drive) is trying to get his career to spark by banging his flinty personality against every hard surface he can find. His plight is like that of Dustin Hoffman’s chronically unemployed actor in Tootsie (1982), the professional who uses dedication to his craft as a justification for being a major pain to everyone he meets. “No one will work with you – you’re too much trouble,” Hoffman’s agent told him, but Llewyn’s manager Mel (the late character actor Jerry Grayson) is less direct; he won’t even give his struggling client a few bucks for back album sales.

In the meantime, Llewyn bounces from one friend’s couch to the next while trying to get paying gigs on a stage or in a studio. There’s work out there, but it always seems to be snatched up first by performers like Jim and Jean (Justin Timberlake and Carey Mulligan), the clean-cut married singer-songwriters whose songs inspire. Llewyn’s oeuvre, by contrast, is more emotionally wrenching: Since the suicide of his performing partner Mike, he’s moved from melodic uplift to darker, powerful songs with titles like “Hang Me, Oh Hang Me.” (T. Bone Burnett, who worked as musical director on the Coens’ O Brother Where Art Thou?, is an MVP here as well.)

Isaac is a revelation as Llewyn, giving us a barely sympathetic lead character with the rough-hewn anti-charm that normally stays on the periphery of a film’s narrative. A less imaginative movie might focus more on Jim and Jean’s marriage – it’s not like there isn’t a story there, what with Jean’s self-hating habit of falling into bed with Llewyn and then yelling at him for it afterward. Instead we’re given a tour of the dark underside of folk music, at a time when the genre was in profound shift from the spirituals of the ’40s and ’50s to the activist anthems of Bob Dylan and Joan Baez. Llewyn’s passion is for music, not politics, which means his entire self-worth rests on fleeting moments like hitting the right note in a performance, or the question of whether he’ll convince a Chicago promoter (F. Murray Abraham) that there’s money to be made in his sound.

The music of Inside Llewyn Davis is worth the price of admission all by itself, but in tone and execution this is a very different animal from O Brother. That film took its characters under a playful arm, and suffused most scenes with a buttery light that just made you feel good. But Llewyn and his onscreen cohorts are alone in the world, and cinematographer Bruno Delbonnel has brought a gray pallor to the film’s look that matches the story’s tone and the cold, wet winter in which its set. Hey, I told you it was a downer – it’s just a downer worth looking up.

(IMAGE: Oscar Isaac in Inside Llewyn Davis. Photo courtesy of CBS Films.)