Angelina Jolie in a scene from Maria. 鈥 IMDB

VENICE 鈥 US actress Angelina Jolie had to learn how to sing opera to prepare for playing Maria Callas, one of the greatest sopranos of all time, saying last Thursday that it was the most demanding role of her career.

Maria, directed by Pablo Larra铆n, chronicles Ms. Callas鈥 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.

鈥淭his is the hardest, the most challenging role,鈥 Ms. Jolie told Reuters ahead of the movie鈥檚 world premiere at the later in the day.

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

Ms. 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 Mr. Larrain that she could sing, but then realized she needed to reach a whole different level, taking seven months out to train for the role.

鈥淚 thought I could sing like people sing in 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鈥檛 really fake opera,鈥 she said.

Mr. Larrain has said that when Ms. Callas is heard in the film in her prime, 95% is taken from the soprano鈥檚 original recordings, but when we hear her at the end of her life, it is mostly Jolie鈥檚 own voice we are listening to. 鈥淪he did a lot of singing lessons, incredibly, and sang from morning to night. We were really touched, we cried during the shoot,鈥 said Alba Rohrwacher, who plays Ms. Callas鈥 adoring housekeeper.

Mr. 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 Ms. Callas鈥 death in 1977 aged just 53.

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

Mr. Larrain鈥檚 previous movies include Jackie and Spencer, biopics about Jackie Kennedy and Princess Diana, other strong women who left their mark on history. Ms. 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.

鈥淚 share her vulnerability,鈥 Ms. Jolie said, alluding to her own troubled personal life, locked in a bitter divorce from actor Brad Pitt, who brought his latest film to Venice at the weekend, ensuring they won鈥檛 cross paths in the lagoon city.

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