Angelina Jolie stopped singing after an ex criticised her voice

She told The Hollywood Reporter: "It was an out-of-body experience because I don't sing.

"I had somebody in my life who was not kind to me about singing. It was a relationship I was in. And so I just assumed I couldn't really sing.

"I'd been to theatre school, so it was weird that it even had an effect on me. I just kind of adapted to this person's opinion. So it took me getting past a lot of things to start singing."

Angelina - who has Maddox, 23, Pax, 20, Zahara, 19, Shiloh, 18, and 16-year-old twins Knox and Vivienne, with Brad - recently thanked her sons for helping ease her nerves about singing in the film.

Speaking at a press conference for the movie at the Venice Film Festival last week, she said: "I was terribly nervous; I spent almost seven months training. My first time singing, I remember being so nervous. My sons were there and they helped to block the door [so] that nobody else was coming in, and I was shaky.

"And [director Pablo Larraín], in his decency, started me in a small room and ended me in La Scala. So he gave me time to grow. I was frightened to live up to [Callas]."

Angelina joked that, after making the movie, she might even get involved in karaoke nights in the future.

Asked if she has a favourite karaoke song, she quipped: "I didn't sing before this [movie] so I haven't done karaoke, but now maybe I have a few!"