How badly did actor and musician John Steven Gardner want a part in “Once,” the Tony-winning stage adaptation of John Carney’s 2007 film about an Irish musician on the skids whose creativity is quickened by a Czech flower girl?

Enough to try to learn to play a dozen instruments in the months leading up to the audition.

Not only did his efforts pay off with a plum role, but the producers made him the “music captain,” or conductor. Not bad for what is essentially Gardner’s first professional job out of Ithaca (N.Y.) College.

“I feel incredibly fortunate,” he said.

Gardner, who grew up in Harrisburg, Va., in the Shenandoah Valley, is earning his Equity union card with “Once,” which opens a return Twin Cities engagement Tuesday at the State Theatre in Minneapolis. While his mother was an opera singer and his father a dentist who dabbled in folk music, he never really thought that his path would lead to the stage. In fact, he rebelled against anything that suggested it, especially music lessons.

“I always hated taking piano — my parents made me do it,” he said. “I didn’t like to practice then or to do much work. Now, of course, I cannot thank them enough. Thank you, Mom and Dad!”

Things started changing for him around age 15, he recalled, when a friend dragged him to an audition for their high school’s production of “Godspell.” After he delivered his first song, the show director, who was the school’s music teacher, asked why Gardner wasn’t in choir.

“I freaked out about that because I was very shy, and my voice had not really changed yet,” he said. But that compliment from his teacher, plus the applause he heard when singing in the ensemble of “Godspell,” got him hooked. Besides, he quickly found, performing was the perfect cure for bashfulness.

Learning instruments

Gardner studied voice, dance and acting in the conservatory program at Ithaca, where he earned a bachelor of fine arts degree.

After graduation, he moved to New York City, joining thousands of wannabes with dreams of Broadway stardom. His was not to end in bitter disappointment, even though he could not land an agent.

When he heard that “Once” was being made into a Broadway musical, he knew that the stars had aligned.

“I just love the movie and watched it obsessively over and over again when it first came out,” he said.

When he found out that the actors would also play instruments, he began to brush up on every instrument he knew.

“I’m proficient on guitar and piano and mandolin,” he said, nodding again to this parents. “So I started learning the ukulele, percussion, melodica, everything I could get my hands on. I became decent at 12 or 13 instruments.”

The auditions were tough, he admitted. He had eight callbacks over a month and a half.

“They kept asking me to try different instruments and I was fearful,” he said. “You’re always nervous at auditions — rejection is a big fact of life in this business — and I sometimes felt like I was going to gag.”

The “Once” creative team obviously liked what it saw. Gardner was cast as Eamon, manager of the recording studio where the play’s Boy and Girl flirt through music. And as music captain, he supervised actors whom he had idolized in other Broadway shows, including Evan Harrington (“Avenue Q”) and Benjamin Magnuson, who was in the “Sweeney Todd” revival headlined by Patti LuPone.

“It was daunting at first, having to give notes to people who’re more established — people I look up to,” said Gardner, who is in his mid-20s. “But after a few months, I got used to it.”

Gardner has been at it for 18 months — including the show’s previous visit to the Orpheum last spring — and he’s grown in the role, said Erica Swindell, who, as dance captain of the touring production, works closely with Gardner to maintain the show’s artistic standards.

“True, John is young, but he’s an old soul who’s wise beyond his years,” she said. “Part of what makes him such a great leader for the show is that he’s steady; he’s knowledgeable, respectful and commanding.”

Gardner said that he’s looking forward to being back in Minneapolis, not least because it’s summertime and everything’s breezy.

“You go to some towns, and there’s nothing to do, so you stay in your room to write music and practice,” he said. “But Minneapolis [and St. Paul] have so much to offer, I try not to get distracted.”