Vadim Rizov’s review published on Letterboxd:
O Brother, Where Art Thou? claimed to be “based upon The Odyssey, by Homer," a link explicitly picked up here when the missing cat Llewyn Davis has been looking for most of the movie returns home — and his name is Ulysses! But the continuity's also musical, Joel Coen told Robert Christgau: “If you trace it back far enough it's all Americana, the same kind of music, the same family tree [...] We felt the folk music revival of the ’50s was in part a revival of the traditional American folk musical forms we'd always been aware of and loved." I wrote a little bit about the Coens' T-Bone Burnett collaborations here, but the bottom line is I think the music in O Brother and The Ladykillers is pretty excellent, while the music in Llewyn Davis is mostly exactly the kind of mediocre garbage you'd expect with a Mumford in the studio. (Sorry to be reflexively hateful about one of the more consistently derided easy targets out there, but that's how it goes.) At PopMatters, Kevin Korber is onto something when he observes "it’s not difficult to see the connections between [the O Brother soundtrack's] cultural moment and the current Mumford-ization of the Top 40" — the bad kind of continuity and influence. It's frictionlessly competent adult contemporary-ish and not very compelling to listen to. There's a little bit of the Coens being kind of Baby Boomer-ish about Real Music (and Bob Dylan!), which is unexpected from such generally unsentimental filmmakers, maybe even a trifle embarrassing.
My musical issues aside (those songs GO ON, and seem foregrounded for their own sake rather than the character's, but their momentum-sapping isn't a dealbreaker), another solid, cruel story about never getting a break, ever, facing down beatings and injustice in an arbitrary, sporadically violent universe with no rules or patterns that can be observed to avoid trouble. Their taste for ornately stylized dialogue locates even the minutest speaking player (the elderly elevator guy kills it) within an ornate form of some kind of cinematic American vernacular, witty sugar-coating for an especially severe worldview with increasingly apocalyptic overtones.