Montreal star conductor Yannick Nézet-Séguin says he employed a secret weapon in teaching Bradley Cooper how to conduct like Leonard Bernstein in the upcoming biopic Maestro: an earpiece.

The Grammy winner, who is currently music director of the Orchestre Métropolitain (Montreal), the Metropolitan Opera (New York) and the Philadelphia Orchestra, says he occasionally had the A-lister don the device so he could guide Cooper through arm and hand movements that would be believable for music-savvy viewers as well as those familiar with Bernstein's distinctive physical style.

Nézet-Séguin served as "conductor consultant" on the upcoming Netflix film, which Cooper co-wrote, directed and stars in, and says there's far more to conducting than just waving a stick around. He says he's seen plenty of movies portray conductors badly, and wanted to ensure Maestro was an accurate depiction of the craft.

The hardest part for most actors, says Nézet-Séguin, is to keep accurate tempo with the baton, especially while the other hand moves fluidly to convey expression.

"I can imagine how it is if there's a movie about tennis and the [actors] hold the racket badly," Nézet-Séguin says during a recent interview about another film he consulted on, Days of Happiness.

Cooper studied videos of Bernstein to nail down the way the West Side Story composer moved his body, but that mimicry only captured part of who the man was, says Nézet-Séguin. When it came to Bernstein's technical prowess, that was trickier to master.

"I was there to actually try and frame it [and say], 'Yeah, but the beat needs to be believable,'" explains Nézet-Séguin. "Because you know, there is a code there. The first beat has to be down, the upbeat has to be up and [to] the side. And this I had to do and help him, guide him on this."

Nézet-Séguin, who also conducted the music for Maestro, describes Bernstein as a longtime "idol."

"He also is very physical and every part of his body is expressing and so I always loved that," he says. "But of course the movie is also about tortured relationships and complicated moments with him being a closeted gay [man] but being married, which is very far from what I am," chuckles Nézet-Séguin, who is openly gay and married to Pierre Tourville, a violist with the Orchestre Métropolitain.

"Different times, that's for sure."

So much has changed about how conductors are perceived as well, adds the 48-year-old Nézet-Séguin, whose bleach-blond hair and navy blue nail polish belie the stereotypical image of the staid and hoary conductor.

Cinema has been slow to catch up to the modern reality, he says, pointing to Tar as especially incongruous to the cultural and social overhaul that he insists orchestra leaders have by and large embraced. Cate Blanchett stars in Tar as an imperious savant who gradually unravels when forced to confront her own toxicity.

The days of the ego-driven, domineering taskmaster are gone, says Nézet-Séguin. "Ahead of its time, I think, conducting had to examine what it is to lead because it's all about emotions — music is emotional."

"So you can't just decide, 'Oh, I'm the traffic cop and it works.' You have to connect to a deeper level," he says. "And therefore you have to accept your own vulnerability as a conductor because you're first and foremost an artist."

To feign perfection doesn't work anymore, he says. "I don't think it ever really worked, honestly."

Maestro opens in select theatres Nov. 22 and hits Netflix on Dec. 20.