"Great Gatsby" actress Carey Mulligan traded in her Tiffany jewels and Prada-designed flapper dresses for polo necks and duffel coats in her second star turn at the Cannes Film Festival Sunday in the Coen brothers' eagerly anticipated "Inside Llewyn Davis".
Mulligan stars with Justin Timberlake and Oscar Isaac as folk singers chasing fame and success in early 1960s New York in a bleakly comic film greeted by one critic as the "best so far at Cannes" while another hailed a "stupendous soundtrack".
The British actress transforms herself into dowdy ratbag Jean, who has just discovered she is pregnant, not by boyfriend Jim, played by Timberlake, but by Llewyn Davis.
"Where were we?" Llewyn asks a furious Jean after he interrupts yet another of her merciless tirades to chase down a street after a cat he has lost.
"You were calling me a careerist and I was calling you a loser," she tells him to laughs from the audience before he sets off on a grim road journey to Chicago in hope of being discovered.
There, the brilliant Llewyn sings his heart out under the stony gaze of a hard-bitten club owner.
As his career dreams slip away, his would-be employer tells him flatly: "I don't see a lot of money here."
All the actors including Isaac as Llewyn sang and played guitar live on set for the film, the Coen brothers' first movie in competition for the Palme d'Or since "No Country for Old Men" in 2007.
Ethan Coen said casting the part of Llewyn had been difficult because only a talented musician and singer who was also an actor would fit the bill.
"That was a casting challenge and we were just -- I don't know how else to describe it -- screwed until we met Oscar," he told reporters on Sunday.
T-Bone Burnett, the film's executive music producer, said it illustrated the hard reality of the music industry and the role luck played.
"You only need a minute. There may be a minute when there may be a reviewer from the New York Times in that particular night and two guys may be playing one after another and one may be tired, may have been beaten down," he said.
"And there might be one guy fresh who comes in and owns that particular moment that the other person might have deserved. I've seen it happen over and over again," he said.
Isaac, Mulligan and Timberlake were joined on the red carpet at the film's premiere on Sunday by US character actor John Goodman, a regular in Coen brother movies.
The film was met with warm applause at a press preview on Saturday.
"What an intense pleasure this film is, one of the Coens' best, and the best so far at Cannes," said the Guardian.
"Above all 'Inside Llewyn Davis' is a revelatory showcase for Isaac, who sings with an angelic voice and turns a potentially unlikable character into a consistently relatable, unmistakably human presence," said US entertainment trade magazine Variety.
The Hollywood Reporter praised a "gorgeously made character study leavened with surrealistic dimensions both comic and dark".
The latest offering from brothers Joel and Ethan was as "stunning and singular as anything in the Coens' canon", it added.
Joel Coen won the Palme d'Or in 1991 for "Barton Fink", and the brothers have made frequent trips to the French Riviera festival with other films selected for the invitation-only competition.
"Inside Llewyn Davis" is Mulligan's second Cannes outing this year after her performance as Daisy in Baz Luhrmann's "The Great Gatsby", which opened the festival on Wednesday.
The 27-year-old, who as a teenager ignored advice to forget acting and "marry a banker", came to the attention of Hollywood after a critically acclaimed debut on Broadway in Chekhov's "The Seagull".
She went on to win a best actress Oscar nomination before she was 25 and has since starred in a string of Hollywood movies including "Drive" with Ryan Gosling.