Bradley Cooper spent six years learning how to conduct a six-minute piece of music for 'Maestro'.

The 48-year-old actor directs and stars in the Netflix biopic as composer Leonard Bernstein and revealed the extreme lengths he went to for a scene that captures his character conducting the 1976 London Symphony Orchestra in Ely Cathedral.

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 made videos with all the tempo changes, so I had all of the materials to just work on."

Bradley – who was joined at the event by co-stars Carey Mulligan and Matt Bomer -explained that he worked tirelessly on the scene as he was "terrified" about not enjoying his performance as the famed composer.

He said: "It was really about dialing exactly what I wanted cinematically and then inviting them to inhabit that space and trusting that they have all done the work. Because I think that I knew, I was terrified, absolutely terrified that if I hadn't done the work I wouldn't be able to enjoy myself in these scenes. And everybody did."