Gary Catona isn’t your garden-variety vocal coach. The man who helped Renée Zellweger channel Judy Garland’s singing style calls himself a “voice builder,” adopting tenor Enrico Caruso’s model of strengthening the muscles that surround the vocal cords. The Philadelphia native’s clients have included Whitney Houston, Andrea Bocelli, Brian Wilson, Steven Tyler, Lenny Kravitz, Liza Minnelli and Shirley MacLaine. He also helped strengthen physically damaged vocal cords for the late Muhammad Ali, who suffered from Parkinson’s, and Jack Klugman, who died of throat cancer. Even Milli Vanilli’s Fab Morvan, famously ostracized by the music industry for lip-synching on the group’s debut album, came to Catona to learn how to sing.

For Zellweger, starring in “Judy” went beyond the complexities of portraying Garland in the last six months of her melodramatic life, a performance that has affirmed the actress’ place on the Oscar front-runner list. She also did her own singing in the film. “Her voice was good before, but now it’s dramatically improved,” says the 67-year-old Catona of working with the Academy Award winner. “Her trick was not impersonating Judy Garland, but bringing something of her own alchemy to it, which I feel she succeeded in doing, while remaining true to the character and making it come alive.”

Catona’s technique is a sort of vocal boot-camp. “Voice teachers tell you to sing through your throat, diaphragm and nose, which is ridiculous,” he says of his “iso-kinetics” method that prevents wear and tear on the vocal cords. “The voice is a muscular phenomenon. My exercises offer the same resistance training, like doing curls with weights.”

Marvels Zellweger: “I never realized that vocal muscles could be manipulated through a particular set of strengthening exercises and was surprised to learn that subconsciously stored emotional components can release as vocal muscles are forced to open.”

The focus for Zellweger was on developing “those broad, round vowel sounds that increased her range,” says Catona. “She really picked up on Garland’s vocal phrasing herself. But she’s a naturally gifted singer. … I just kept her voice in optimum shape, giving her little tips to help.  Her performance was all about the individual emotional interpretation and authenticity.”

Catona was introduced to Zellweger by her boyfriend, guitarist Doyle Bramhall II, who sought out his vocal training on the recommendation of fellow client Boz Scaggs. Bramhall served as a back-up vocalist for Eric Clapton and Roger Waters. And their relationship went beyond the screen to recording sessions for the film’s soundtrack, released in September 2019 by Universal Music Group’s Decca Records. The collection includes duets with Sam Smith (“Get Happy”) and Rufus Wainwright (“Have Yourself a Merry Little Christmas”) on which Zellweger’s singing is more supple and brighter.

“It was joyful to experience the unexpected transformations that manifested in the process of finding and reclaiming my voice,” says Zellweger. “I am really grateful to Gary. The shared work has been an enormous blessing that I continue to carry with me.”