'West Side Story': Steven Spielberg says his first musical was a 'steep learning curve' (exclusive)

Watch: Steven Spielberg on the challenges of making his first musical

You'd be forgiven for thinking that, after 50 years in Hollywood, Steven Spielberg doesn't get nervous when he steps on to a set for the first time.

But the 74-year-old movie maestro has confessed that he did have some trepidation about West Side Story, which is his first attempt at an all-singing, all-dancing big screen musical.

Spielberg has said that his take on the musical draws more from the original 1957 Broadway show than it does from the Oscar-dominating 1961 movie adaptation, telling the love story between white New Yorker Tony (Ansel Elgort) and Puerto Rican Maria (Rachel Zegler) at a time of fraught racial tension.

Read more: Rita Moreno returns in trailer for Spielberg's West Side Story

The director told Yahoo that the project was a challenging one, but he was relieved to have a lengthy rehearsal period to get the musical sequences right.

"I had never spent four and a half months in rehearsal," Spielberg told us. "It was the most valuable four and a half months I've ever spent because I was able to get on a very steep learning curve, having never made a musical before," said Spielberg.

"I had four and a half months to watch all of the different dancers and Justin Peck, the choreographer, putting all of the dancers together.

"I was able to integrate my camera, which I always considered to be one of the dancers, not just looking at the dancing from afar but being inside of the numbers.

Read more: West Side Story praised for not subtitling Spanish dialogue

"I was able to experiment, often using just a video camera to run around and putting these sequences together on video and then putting the music to it and making all of my mistakes during rehearsal. It was one of the most valuable periods of time.

"By the time we began shooting the film, I was still nervous being a novice musical movie director, but I had a lot more confidence because of all of the preparation I had given myself."

Spielberg has often maintained that his 1975 breakout movie Jaws remains his most challenging work, but how does that compare to the musical complexity of West Side Story?

"I got to tell you, I had so much more control over West Side Story than I did over Jaws," said Spielberg.

Read more: Ian Shaw on playing his father in Jaws play The Shark is Broken

He added: "Mother Nature directed me and basically the mechanics of never having made a 26-foot long mechanical shark and stick it in the middle of the Atlantic Ocean. Those were both self-defeating prophecies.

"It's amazing we survived and that the movie survived as a film. But I had a lot of control on West Side Story, so I can't even compare them like apples and oranges."

West Side Story dances its way into UK cinemas from 10 December.

Watch: Trailer for West Side Story