Angelina Jolie's voice soars for Maria Callas Venice movie

U.S. actor Angelina Jolie had to learn how to sing opera to prepare for playing Maria Callas, one of the greatest sopranos of all time, saying on Thursday that it was the most demanding role of her career.

"Maria", directed by Pablo Larraín, chronicles Callas's final days in Paris when she was addicted to anti-anxiety drugs. It recalls the high and low notes of her tumultuous past when she wowed audiences around the world with her astonishing voice.

"This is the hardest, the most challenging role," Jolie told Reuters ahead of the movie's world premiere at the Venice Film Festival later in the day.

"I was like on another planet because it was so beyond what I was comfortable with as a person and as an artist," she said, recalling scenes shot at Milan's famous La Scala opera house.

Jolie has appeared in more than 60 films, including action-packed blockbusters and emotionally charged dramas, winning an Oscar for Best Supporting Actress for her role in the 1999 movie "Girl Interrupted".

She had told Larrain that she could sing, but then realised she needed to reach a whole different level, taking seven months out to train for the role.

"I thought I could sing as people sing in the film, you pretend to sing or you sing a little. And it was very clear early on that I was going to really have to learn to sing because you can't really fake opera," she said.

Larrain has said that when Callas is heard in the film in her prime, 95% is taken from the soprano's original recordings, but when we hear her at the end of her life, it is mostly Jolie's own voice we are listening to.

"She did a lot of singing lessons, incredibly, and sang from morning to night. We were really touched, we cried during the shoot," said Alba Rohrwacher, who plays Callas' adoring housekeeper.

Larrain said he had grown up listening to opera and hoped his latest film would encourage people to explore an art form that has lost much of its public appeal since Callas' death in 1977 aged just 53.

"We really hope this movie creates an interest towards opera, whatever the number of people, be it five people, 10, a million or more," he said.

Larrain's previous movies include "Jackie" and "Spencer", biopics about Jackie Kennedy and Princess Diana, other strong women who left their mark on history. Callas was one of the biggest stars of her day but lived her last years in isolation, deserted by her great voice and her lover Aristotle Onassis.

"I share her vulnerability," Jolie said, alluding to her own troubled personal life, locked in a bitter divorce from actor Brad Pitt, who is due to bring his latest film to Venice at the weekend, ensuring they won't cross paths in the lagoon city.

Larrain said Callas had a tragic sense of life, with 90% of the opera she sang on stage ending in death. "She slowly became the sum of the main tragedies she sang," he said.

"Maria" is one of 21 movies competing for the prestigious Golden Lion award at the Venice Film Festival, which runs until Sept. 7.