Justin Timberlake at the photo call for the Coen brothers' "Inside Llewyn Davis" on Sunday (Photo: Mehdi Chébil)

Cannes is always a bit of a roller coaster of delights and disappointments, pleasures and frustrations.

Just when I was starting to feel down about the competition (two fine filmmakers, Kore-eda Hirokazu and Arnaud Desplechin, filed weaker-than-average entries this weekend), the Coen brothers came to the rescue with their gorgeous “Inside Llewyn Davis”, a razor-sharp deadpan comedy suffused with sorrow about a struggling folk singer in early-1960s New York.

I’m not an unconditional fan of the Coens, who sometimes treat their characters with smarter-than-thou condescension that can make their films feel like cold, hermetic exercises in irony (“Burn After Reading” is a prime example, and their 1991 Palme d’Or winner “Barton Fink” isn’t far off).

But their new movie ranks with their very best (“Fargo”, “No Country for Old Men”, “A Serious Man”) in its nearly pitch-perfect balance of biting satirical humour and deep reserves of feeling. The film’s protagonist (played by singer-actor Oscar Isaac in a star-making, award-worthy turn) embodies the tricky duality of cruelty and tenderness that makes “Inside Llewyn Davis” such a treat. Navigating his mess of an offstage life -- couch-hopping, mooching, and wrangling with his scam artist manager and another folk singer who may or may not be carrying his child (Carey Mulligan, radiating fury tinged with longing in a marvellously vivid comic performance) – Llewyn Davis is a schlumpy, scowling grump. But when he performs (glorious folk tunes arranged by T-Bone Burnett and sung live on set), revealing a honeyed, slightly raspy voice, his face mellows, his eyes close, and he seems to be opening his soul to the world. This jerk’s music is his redeeming feature.

Indeed, the folk songs in “Inside Llewyn Davis’ (even the ones the filmmakers mock affectionately), with their yearning lyrics and melancholy melodies, don’t just offset the dry, Coen-esque wit of the screenplay; they give the movie a rich emotional subtext, allowing the characters’ often laugh-out-loud gripes, swipes, one-liners, and accusations to echo with hints of regret and desire.

As Llewyn Davis fights to kick-start his floundering career, scrape together money without sacrificing his ambitions, get along with the people in his private and professional lives, and keep track of a cat he inconveniently finds himself caring for, we come to understand that the movie is a comedy about loss and letting go: of an artistic partner, a love interest, a childhood dream.

As usual, the Coens find a fitting visual match for their themes: cinematographer Bruno Delbonnel uses wintry whites, greys and browns, and repeated shots of hallways, long subway cars, and empty stretches of highway suggest the title character’s existential anxiety.

Such images feel just right for a film that’s not just a meditation on art, failure, responsibility, and self-acceptance, but also a portrait of a specific American cultural moment -- at the start of the Vietnam War -- when young people were facing stark choices of identity and values.

Along the way, “Inside Llewyn Davis” features one of the most sublime sequences the Coens have ever shot, involving a snowy highway in the middle of the night, that pesky cat Llewyn looks after, and a snippet of opera playing on the car radio.

The film also flaunts a uniformly superb ensemble, with Justin Timberlake, John Goodman, Garrett Hedlund, Jeanine Serralles, Max Casella, Stark Sands, F. Murray Abraham, Robin Martlett, and Adam Driver (of hit series “Girls”) delivering jewel-like supporting performances.

We haven’t even reached the festival’s halfway point yet, so it’s far too early to start talking about the Palme d’Or. But “Inside Llewyn Davis” is the best thing I’ve seen at Cannes so far this year.