'La La Land' director Damien Chazelle reveals surprises about the film's elaborate opening scene

— -- “La La Land” director Damien Chazelle, the youngest person ever to win the best director award at the Golden Globes, said the film’s elaborate opening scene almost wasn’t included in the final cut.

“We did it, we always wanted to do it, but then when we were editing the movie it seemed to not work for a long time,” Chazelle, 32, said on “Good Morning America.” “There was stuff around it, we were like, 'Ah, this isn’t really getting us into the world of the movie the way we needed it to.' At first we thought the scene was the problem, so for about four months or so the movie just didn’t have that number in it.”

The alternative opening scene “started with a little bit between Ryan [Gosling] and Emma [Stone],” he explained.

Chazelle said it’s “tough to describe” why the theatrical dancing and singing number wasn’t working in the movie.

“It’s part of the pain and the joy of making a movie,” he said. “A lot of it you can’t really explain. You just sit and watch and something feels right or it feels wrong. I found it really helpful to invite friends over to the cutting room to watch scenes or watch the movie, and mainly just watch them watch it. You can see where they’re twitching in their seat, where they’re kind of recoiling, where they’re leaning in. That tells you everything.”

Being able to stop traffic on a freeway in Los Angeles for an entire weekend was also no easy feat.

“I alone could never have done that,” said Chazelle. “It was an incredible team of my choreographer, Mandy Moore, a different Mandy Moore than some people think, and then the whole crew on the movie. They managed to convince the city to let us shoot on this freeway overpass ramp for two days on a Saturday and Sunday."

“We went in at the dead of night, piled all the cars in there,” he added. “The crew got it all ready. We started rehearsing at dawn and as soon as the sun is high, you start shooting and then you just try to cram it out until the sun sets again.”

Chazelle is poised to win best director at the Oscars as well, with “La La Land” earning a whopping 14 nominations. He also directed “Whiplash,” which gained a lot of attention during the last awards season.

J. K. Simmons, who won best supporting actor for his role in “Whiplash,” had a special message for Chazelle ahead of the upcoming Oscars.

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JK Simmons' message for 'La La Land' director

Oscar winner J.K. Simmons sent "GMA" a special message for his "Whiplash" and "La La Land" director, Damien Chazelle.

ABCNews.com