LOS ANGELES – American actor Bradley Cooper did it all for his new musical biopic Maestro.

Now available on Netflix, the film charts the whirlwind romance between legendary American composer and conductor Leonard Bernstein (Cooper) and his wife, Costa Rican actress Felicia Montealegre (Carey Mulligan).

Cooper also spearheaded and directed Maestro, co-wrote the screenplay and even learnt to conduct an orchestra for some of its scenes.

Speaking at an event in Los Angeles, he says it felt like he had a strange connection to the late icon, who died in 1990 at the age of 72.

“This didn’t really feel like film-making as much as it was a ritual – a sort of channelling.

“And that was very early on. I could just feel him,” says the 48-year-old star, who received Oscar nominations for his performances in dramas such as Silver Linings Playbook (2012), American Hustle (2013) and American Sniper (2014).

“I swear I knew him. This movie has messed time up for me. It’s bent time, it really has.”

For the film’s soundtrack, Cooper – who also directed and starred in another musical romantic drama, the Oscar-winning A Star Is Born (2018) – incorporated some of Bernstein’s compositions.

The composer was best known for writing the music in the Broadway musical West Side Story, the score for the acclaimed crime film On The Waterfront (1954) and several symphonies, and some of these can be heard in Maestro.

Cooper did not want to make a traditional biopic of the man “just because he’s the most photographed and documented musician, maybe of all time, and many very good documentaries have been made about him”.

“But I did want to serve his legacy musically,” he says. “And I thought the best thing is to tell a story we can all relate to, hopefully, and it’s all to the rhythm of his music.

“So, the movie is all scored to his music and that, to me, is the best way I can present to you this man’s beauty and his gifts.”

It was Cooper who secured the rights to tell Bernstein’s life story, and one reason was the actor’s lifelong fascination with conducting, dating back to when he was a child.

“I asked for a baton for Christmas.

“I used to watch those Looney Tunes cartoons with Bugs Bunny conducting and I spent, embarrassingly, too many hours just pretending I was doing that as a kid – and into my adolescent years, maybe even college.

“And I had that baton till I lost it a year ago. But my daughter just asked me for one for Christmas, which is hilarious,” he says of five-year-old Lea De Seine, his child with former girlfriend and Russian model Irina Shayk, 37.

“So, I had all these years of being obsessed with it, and I think that made it easier for me to go on this beautiful journey as Lenny (Bernstein).”

Cooper did not, however, shy away from exploring the complexity of Bernstein’s character and his complicated relationship with Montealegre.

She married him knowing he was bisexual and tolerated his affairs, including the one he had with the late American clarinettist David Oppenheim, played by Matt Bomer in the film.

But she loved Bernstein and went on to have three children with him – all of whom have given this film their blessing, Cooper says.

“Truth is the thing that lives, and these incredible actors just brought truth to the film.”

This was one reason Bernstein’s children, now aged 61 to 71, opened their homes and hearts to Cooper as he told their parents’ story.

“The kids, early on, took a chance with me because I didn’t know what I was going to write at the time that they gave us the rights to the music.

“And when I first came to them and said, ‘I want to make a movie about your parents – and your mother’, they were really shocked. I don’t even know if they really believed that it was going to be a movie very focused on Felicia.

“So, I think they were very happy that we were able to unearth this incredible woman for you all to see and get to know,” Cooper says.

• Maestro is available on Netflix.