Bradley Cooper was in character as Leonard Bernstein for a year before shooting Maestro

Bradley Cooper was in character as Leonard Bernstein a year before shooting his biopic 'Maestro'.

The actor plays the legendary composer in the film which he wrote and directed acting opposite Carey Mulligan who played Bernstein's wife Felicia Montealegre - and Carey has revealed Bradley was speaking in the composer's voice in phone calls to her 12 months before they started filming.

She told Variety: "He did so much prep. He prepped to the point where he walked on set and didn’t have to think — like you say. And I think to be able to direct it and write it and star in it and all that stuff, he needed to get everything out of the way. So he was ringing me a year before in full Lenny voice and everything."

She added: "I’d be putting the kids to bed, and I’d get a FaceTime with him as Lenny: 'OK. Call you back, mate!'"

Carey added of the Netflix movie: "When he [Bradley] first offered me the job, he was like, 'I want you to do this, but sort of on the proviso that you go and really give it everything'. Which I immediately thought in my head, 'Not all in'.

"There was something about it. I thought, 'Oh, crikey, that’s playing a real person.' And playing someone who does have this quite interesting dialect. And there’s a real responsibility to their children who are a big part of this process. It was huge. But that was actually the only way to do it, was just to do the whole thing."

It comes after it was revealed Bradley was so devoted to the part of Leonard Bernstein he spent six years learning how to conduct a six-minute piece of music for a scene in the film in which he worked with a real orchestra.

Speaking at a Q and A in New York City, Bradley said: "That scene I was so worried about because we did it live. That was the London Symphony Orchestra. I was recorded live, I had to conduct them. And I spent six years learning how to conduct six minutes and 21 seconds of music."

The 'A Star Is Born' actor thanked his "wonderful teachers" for helping him to recreate Bernstein's style with the baton. Bradley explained: "I was able to get the raw take where I just watched Leonard Bernstein (conduct) at Ely Cathedral with the London Symphony Orchestra in 1976. And so I had that to study. "And Yannick Nezet-Seguin [Music director of the Metropolitan Opera] made videos with all the tempo changes, so I had all of the materials to just work on."