April 25, 2016 at 08:26 PM EDT

Meryl Streep has shown off her pipes in movies like Mamma Mia and Into the Woods, but to play the titular socialite in Florence Foster Jenkins, Streep had to face one of her greatest vocal challenges yet: emulating the worst opera singer of all time.

Florence Foster Jenkins tells the story of a real-life New York heiress, whose love of opera was only exceeded by her complete lack of talent. When the wealthy Jenkins decides that she wants to perform at Carnegie Hall, she recruits her husband, St. Clair Bayfield (Hugh Grant), and an accompanist, Cosme McMoon (Simon Helberg), to help make it happen.

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In this new making-of featurette, the cast discusses the real Jenkins — and Streep’s intentionally dreadful performance.

“The first time I heard Meryl, it was up there among the funniest things I’d ever heard,” Grant says. “Not just bad, but hilariously bad. Pure genius.”

Florence Foster Jenkins hits theaters on Aug. 12.

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