A secret center of the musical theater universe lies almost 3,000 miles from Broadway in a modestly grand house in Toluca Lake. On a late summer day, the home’s most striking feature was the figure of a white standard French poodle. Visible through one of the windows flanking the front door, she sat so still that she might have been mistaken for a statue, like the lion-dogs that guard the entrance to a Shinto shrine.

If musical theater had a canine sentinel, it might well be a standard French poodle. But no. When the door opened, the dog, Belle, sniffed politely before trotting deeper into the house, neon-green-painted nails flashing, to pause briefly beside her owner: Eric Vetro, perhaps the leading vocal teacher and trainer of bold-faced names on stage and screen, including several of the leads in the upcoming film adaptation of “Wicked.”

Ariana Grande, who plays Galinda, has spoken often and at length about how long and how rigorously she worked on raising her pitch and honing her voice before auditioning for her dream role — and Vetro is the man who coached her.

Just as he coached Jonathan Bailey for his role as Fieyro. Just as he worked with Jeremy Allen White for his performance as Bruce Springsteen in the upcoming “Deliver Me From Nowhere” and Timothée Chalamet for “Willy Wonka” and the upcoming Bob Dylan biopic, “A Complete Unknown.” And Renée Zellweger for her Oscar-winning performance as Judy Garland in “Judy.” And Lea Michele for “Funny Girl,” Austin Butler for “Elvis,” Josh Gad for “The Book of Mormon” and “Frozen,” Emily Blunt for “Into the Woods” and “Mary Poppins Returns,” Emma Stone and Ryan Gosling for “La La Land” and Halle Bailey and Melissa McCarthy for “The Little Mermaid.”

The list goes on and on and on. It also includes plenty of equally well-known recording artists, such as John Legend, Shawn Mendes, Katy Perry and Pink. Indeed, if a famous actor or singer refers to the work they’ve done with a vocal coach, there’s a very good chance they are talking about Vetro. Invariably in very glowing terms.

“Even though my range has always been high soprano,” Grande says via email, “Galinda requires a very different technique, and has a very different sound than the one I use to sing my pop music. Her voice is classical and operatic, and I had the honor of working on that every day together with Eric in preparation. [He] would paint Belle’s nails pink and green and put little pink ribbons in her hair to send me off before each audition or callback,” she adds. “Not only is he the best at what he does but he is truly the most thoughtful and kindest man in the world.”

Dressed, on this day, in black Prada jacket and shoes, which match his meticulously groomed short beard and hair, Vetro, 68, is an arresting figure, with a ready and dazzlingly white smile and the slender, expressive hands of a piano player. That’s how he got into music, initially — he’s played piano since he was 5. A voice major at New York University, he worked in cabaret for many years, learning, he says, the valuable lesson of listening, both to what a person’s voice can do, and also to what it should do.

“So many young girls can belt it out and they get known for having a big voice. But that cheats them. You have to listen carefully and adjust, get them to understand that some voices are more beautiful when they’re not bigger.”

His work as a musician, teacher and adviser led him to L.A., where, he says, “I kept meeting people and getting coaching jobs. If you throw yourself into it 100 percent, you’re going to get noticed.”

In the beginning, most of his clients were outside the entertainment industry: nurses, waiters, people who just wanted to sing better. Then he got hired by Craig Zaden and Neil Marin to work on the 1999 remake of “Annie,” which led to “Chicago,” “Hairspray” and “Hairspray Live.” He began working with Bette Midler during her Vegas residency, Hugh Jackman on “Boy From Oz” and Grande, who began working with Vetro when she was 23. “Once you get going,” Vetro says, “it just snowballs. Now I don’t work with ‘regular’ people at all.”

Now he works on movies, theatrical shows, musical tours, brought in by directors, producers and musical directors to work with performers with a variety of experience levels and demands — singers, like Grande, moving into musical acting roles; actors, like Blunt, in their first singing roles; artists on tour, and performers who are looking to grow their voice or achieve a specific sound.

For actors like Butler, White, Zellweger and Chalamet, who need to channel a well-known voice the first step is being aware of the voice they have.

“We start with voice lessons so they understand their own voice,” Vetro says. “Then we start with the realm of another voice. It might be pronunciation, or where they take their breaths or the accent. We start vocalizing in character — I asked Renee, ‘What would Judy think of this exercise?’”

The goal is to capture the essence of the person, he says. “You don’t want it to be an impersonation.”

Vetro says he has only turned one client away — a well-known model who had been offered a role on Broadway. “He was very good-looking, charming. And then he opened his mouth. I said, ‘If this were a movie, maybe, but for you to sing on Broadway is never going to happen.’ His girlfriend called me later to thank me.”

Thanks to a recently released BBC Maestro series, however, “regular people” can get the Vetro treatment. He is filming it on this particular summer day, on which his home is filled not just with two pianos and multiple keyboards, but also lights, cameras and sound equipment.

For about 30 minutes, he works with longtime students, singer-songwriter Heidi Webster and singer-actor David Burnham. Burnham, who played “Wicked’s” Fiyero on Broadway, started working with Vetro after he was cast in a Universal Studios theme park show. “Eric realigned my voice,” he says. “I have recordings of him doing lessons that I use before every Broadway show.”

Vetro with students Heidi Webster and David Burnham.

(Dania Maxwell / Los Angeles Times)

“Lessons” include singing scales with one’s hands in the air, dropping on the high note, or bending forward and being pulled up by the ascension of notes.

“We’re like athletes,” Burnham says. “Runners don’t race without warming up.”

There’s also a lot of breathing exercises — the famous “hee hee heeee,” jaw-dropping, face-wagging, arm-waving and humming through a straw, sometimes into a cup of water.

“It’s amazing what you can do with a straw,” says Jonathan Bailey via email. “I thought we elevated it two levels when instead of using a cup of water we used champagne flutes, which I just thought was the height of sophistication. He always had a naughty twinkle in his eye and we laughed and laughed and laughed.”

In preparation for “Wicked,” Bailey began working with Vetro, often over Zoom, while still filming “Fellow Travelers.”

“A real challenge for me was that I was filming in Canada and London and going back and forth. With ‘Fellow Travelers,’ I’d do 21-hour days where I’d either have to shout or sometimes I’d have to smoke,” he says. “[Eric] sees you at all different moments of the day and in all different levels of excitability. It’s amazing, you start in your sort of home setting with him and build such a kinship and make such a friendship that he becomes sort of a spiritual guru.”

Vetro’s love of his clients and craft is palpable. The walls of his studio are papered with photographs of his students (and their various awards), and the fondness with which he speaks of them appears to be boundless and utterly sincere; he radiates positive energy. He needs to — being the entertainment industry’s go-to vocal coach is not a 9-to-5 gig. Vetro works pretty much round the clock, often consulting in several time zones. After filming the BBC piece and doing this interview, he will work with one student in Australia at 5 and another, in London, at 11.

Friends tell him he needs to take a vacation once in a while, he says, but he has no interest. There’s always, as they say, another opening, another show.

“I just love it so much,” he says. “It does not feel like work. I’d rather do this than anything.”