How Renée Zellweger became Judy Garland: High heels and feathers, anyone?

To portray Judy Garland on screen, Renée Zellweger meticulously studied live recordings and archival footage of the Hollywood icon.

“We were mining for treasure,” the actress told The Times of making “Judy,” which hits theaters Sept. 27.

It’s a process that included a bit of experimentation to find what is “recognizable in terms of Judy’s features, in defining characteristics, in terms of her body language and her performance language, and what we recognize as iconic and her physicality,” Zellweger explained at the Toronto International Film Festival. “We would find these little things and go, ‘Yeah, that, that, keep that, keep that.’”

Directed by Rupert Goold, the drama centers on the Hollywood icon juggling her personal and professional struggles while performing a five-week run in 1968 London near the end of her life.

On set, Zellweger was always listening to Garland’s voice via headphones. And when she needed to get into character, she’d repeat what Goold called “trigger phrases,” or “a couple of these Judy phrases again and again to get the voice in the right place.”

Zellweger then demonstrated her technique, repeating signature deliveries from Garland’s notable performances and talk show appearances. Among them: “feathers,” “high heels” and the sentence “I must sit down.”

“It would set things in the right place,” she explained. “There was a long list of those to make sure that we were in the right place that day.”