Nothing will bring a smile to your face faster this holiday season than the opening number of “La La Land,” Damien Chazelle’s new movie that’s poised to reinvigorate the Hollywood musical.

The scene is a traffic jam on a Los Angeles freeway. It’s sunny — it’s always sunny in LA — but the drivers are hermetically sealed off from the weather, from each other, in their air-conditioned cars. Horns honk, windows roll down, music drifts from radios. And then, for no apparent reason, a woman jumps out of her car, throws her arms open to the sun and starts singing. Soon everybody’s singing and dancing around and atop their cars. An exasperating traffic jam turns into a big, bold, bright showstopper.

The scene evokes Gene Kelly and Cyd Charisse, “Seven Brides for Seven Brothers” and “An American in Paris.” Throw in nods to “The Umbrellas of Cherbourg” and “The Young Girls of La Rochefort” — director Jacque Demy and composer Michel Legrand’s charming French movie musicals of the 1960s — and you have cinematic confection.

Chazelle had those performers and movies in mind when he made “La La Land.”

“I fell in love with live-action musicals — with Fred Astaire and Ginger Rogers, Gene Kelly — when I was 18,” says Chazelle, who grew up in Princeton, NJ. “I loved the creative bravado. When someone starts singing, those movies just jump to a whole new resister, unapologetically. Not everything has to be grounded in psychological reality. If you’re happy enough, you break into song. That was par for the course in old Hollywood, and I wanted to get back to that simplicity.”

Caught in the traffic jam are the movie’s stars, Emma Stone, as a struggling actress, and Ryan Gosling, a down-on-his-luck musician. He honks at her. She blows him off. But in true old Hollywood fashion, their paths cross again. On their first date, when love comes in and takes them for a spin, they dance among the stars at the Griffith Observatory in Los Angeles.

“La La Land” received rave reviews at the Venice Film Festival last summer and is generating strong Oscar buzz. But the movie almost didn’t take flight. When Chazelle brought the idea to Hollywood executives, he was greeted with skepticism. “Chicago” won six Oscars, including Best Picture in 2003, but it was based on a hit Broadway musical that everybody knew. “La La Land,” an original film musical, would be expensive, with no guarantee that contemporary audiences wouldn’t smirk at singing and dancing from the Golden Age of Hollywood.

“I think they crunched the numbers in the backroom and saw that it just didn’t add up,” says Chazelle. “It may be phony math, but there’s a certain kind of logic to it.”

Chazelle switched gears and made a small, dramatic movie instead — “Whiplash,” which won three Oscars, including Best Supporting Actor for J.K. Simmons. (Simmons has a charming cameo in “La La Land.”) Chazelle now had clout with the studios, and could start peddling “La La Land” again. He found the perfect producer in Marc Platt, a musical theater fan who, when he wasn’t producing hit movies such as “Legally Blonde,” brought a little show to Broadway in 2003 called “Wicked.”

It has grossed, to date, more than $4 billion worldwide.

“I loved ‘Whiplash,’ so it’s probably true that had Damien come to me with the phone book, I would have produced it,” says Platt. “But I believe in film musicals — ‘The Sound of Music’ tells its story beautifully — and when Damien walked me through his script shot by shot, it was clear he was lovingly looking back a the old musicals but also stretching the form.”

For all its spontaneous singing and dancing, “La La Land” has a naturalistic look. Los Angeles, the movie’s ever-present backdrop, is both romantic and gritty. In one scene, a group of girls in brightly colored dresses are singing and dancing down their way down an LA street. There’s a palm tree, but look closely at the street and you’ll see oil slicks and cracks in the pavement.

“I have a love-hate relationship with Los Angeles,” says Chazelle. “It seduces me at one moment and then utterly crushes me and disgusts me at another. That alone is fodder for a musical.”

“Astaire and Rogers. Hepburn and Tracy. They had chemistry. Emma and Ryan have it, too. It’s old-school and wonderful.” - Producer Marc Platt

The characters portrayed by Stone and Gosling experience the seduction and disappointment of the LA dream factory. Their love affair takes some unexpected twists, but their attraction for each other is always palpable.

“There is a quality to Emma and Ryan that is old-fashioned Hollywood,” says Platt. “Astaire and Rogers. Hepburn and Tracy. They had chemistry. Emma and Ryan have it, too. It’s old-school and wonderful.”

Stone and Gosling had some experience singing and dancing. She did a nice turn as Sally Bowles in the Broadway revival of “Cabaret” a couple of years ago, while he got his start on the Disney Channel’s reboot of “The Mickey Mouse Club” in the early ’90s. But it’s fair to say neither was the modern-day incarnation of Charisse and Kelly. So they went to work in the rehearsal studio with “La La Land” choreographer Mandy Moore.

“I worked with them separately at first, because I didn’t want it to be the blind leading the blind,” Moore says. “I wanted to build up their confidence. You don’t want someone else in the room giggling at you because you can’t pick it up right away.”

As it turned out, Stone was a quick study, nailing the routines and then, later, adding nuance. Gosling was slower, but, says Moore, added his personal style right away. When she put them together, they clicked.

When you see them on-screen, a Rodgers and Hart line is sure to cross your mind: “Isn’t it romantic?”

If “La La Land” is a hit, is a Broadway stage version a possibility?

“Certainly, when I’m involved,” says Platt.

Chazelle says, “I would be scared out of my mind. I’ve never done theater. I have no idea what I would do with it onstage. But never rule anything out.”