Kalas was an American-born Greek soprano and one of the most famous opera singers.
In Maria, the singing scenes use a mixture of Jolie’s own voice and Kalas’ original recordings.
The actress learned to sing opera for the role, which she describes as “very physically demanding.”
According to her, the training took about seven months.
“We started with regular singing classes and it was challenging in a lot of ways, but when you started with opera classes, the things that are required of your breath and your body and just the power of what you’re pushing through yourself, it’s just a whole different physicality.”
Jolie, whose previous film credits include Changeling, Maleficent, Salt and Mr. and Mrs. Smith, said she had never sung before and was “actually very shy to sing.”
“It was probably one of the areas of my life where I was hesitant,” she said.
But she noted that it’s also something she enjoys.
“One of the greatest privileges of being an actor is that you often have the support of a team to try things and explore things you’ve never done before, and that was definitely the most challenging thing,” she said.