Angelina Jolie "didn't really think" she'd have to sing in 'Maria'.

The 49-year-old actress portrays opera singer Maria Callas in the biopic but didn't really register everything she'd need to do to play the soprano until she had her first lesson with a music teacher.

She recently told Best magazine: "I made the mistake in the beginning of thinking, when he asked me to sing a little, 'I like movie singing.'

"I could sing a bit I guess.

"I very quickly realised that you can't fake sing opera. Not that I wanted to fake sing anything, but I didn't really think I was going to be asked to actually sing.

"Somehow, it didn't cross my mind. I don't know why.

"I didn't completely understand until I was standing in this room and Pablo (Larrain, director) had met so many different teachers and he found one to begin."

And Angelina "started crying" as soon as she had to sing during that first lesson.

She added: "The first time, he said, 'OK. Plant your feet'…

"He took me seriously as a singer, which was very moving to be already.

"He said, 'Take a deep breath and then start to make sounds' - I started crying.

"Because I think we all hold so much in that we don't really let out.

"We don't let our full voice out."

The 'Maleficent' star - who has Maddox, 23, Pax, 21, Zahara, 19, Shiloh, 18, and twins Knox and Vivienne, 16, with ex-husband Brad Pitt - knew she was making progress with her vocals according to how her kids reacted.

She said: "I think I knew when I got better, because I think in the beginning it was more like they were proud of me for trying so hard.

"It wasn't, 'We like your voice'. It was like, 'Good for you, we're proud of you Mom. We know how hard you're working.'

"Then there was a time when they started to say, 'Actually, hey, you're kind of doing it Mom.'

"So they were with me through the times when I was singing loud in the house - and everybody was probably in their rooms thinking, 'Oh my god.' You know, it's like learning the violin at home."