Inside the movie 'La La Land' with the film's choreographer, Mandy Moore

HOLLYWOOD, California (WABC) -- If you've seen 'La La Land', you've seen her work.

She's the woman who taught two actors how to tap dance, and who staged a whole scene on an L.A. freeway.

Now, choreographer Mandy Moore is taking us inside the movie.

They made magic in 'La La Land', during what's called the magic hour after sunset. But with each take lasting six and a half minutes, Emma Stone and Ryan Gosling could only do it a few times before losing the light.

"You know we had to get it as perfect as possible so we practiced for about 3 months beforehand," said actor Ryan Gosling.

They practiced with choreographer Mandy Moore for all the dances in the film.

"These are not people that grew-up dancing every day, you know, and that's what I find fascinating is that they were able to get to that level of movement with not really being professional dancers," Mandy said.

Like 'Mia' in the movie, Mandy came to 'La La Land' with a few bucks and a big dream. She was mentored by Carrie Ann Inaba, and ended up working on 'Dancing With the Stars' before branching out into movies.

"I learned how to rehearse with A-list talent and how to push them," she said.

We met at NeueHouse in Hollywood so Mandy could show me how Ryan learned one step at a time.

"Ready and, 5,6,7, here we go. One, 2, 3 now step. That's it!", she said as she taught me the dance.

The movie's opening number began with a single instruction from writer/director Damien Chizelle.

"I want to do this amazing number on a freeway, now everybody just go and do that!", said Mandy.

She began by making sketches showing where the cars and cameras would be. During filming, Moore was hidden under one of those cars.

"I had to be off camera, but I had to be very close to the talent because as a choreographer obviously on set you're in charge of making sure people hit the things they need to hit," said Mandy. "I mean I still get goosebumps when I think about it."