Immersing itself in the aural plane—and sometimes in the absence of it—undertone becomes a rare genre exercise where what you hear is often more terrifying than what you see.

For Tuason and stars Nina Kiri and Adam DiMarco, that approach meant building a horror film that relies less on personified monsters and more on something amorphous and invasive—forces that creep into every dimension and evade the limits of human perception.

It’s a fitting strategy for a film centred on Evy (Kiri), a perpetually headphone-clad investigative podcaster who discovers a series of deeply unsettling recordings. As she cares for her terminally ill mother and listens to the sound clips with her co-host Justin (DiMarco), ancient and primordial terrors begin bleeding into the present through modern technology.

Connecting with RANGE just shy of the film’s release—following rollicking premieres at Fantasia and Sundance—the trio agrees that the film’s sound-first philosophy is essential to its lingering sense of dread.

“You’re always afraid of what’s behind you,” says Tuason. “You’re always looking over your shoulders, and you can’t do that just on the screen, which is always in front of you.”

He continues, “I approached this with the intention of creating a soundscape… that’s another dimension, right? It’s the scariest one because it’s all around you.”

With such emphasis on sound, films like The Conversation naturally come to mind, where audio manipulation twists a portrait of paranoia and alienation. But for Tuason, the terror of silence proved just as influential.

“I looked at 2001: A Space Odyssey, and its use of silence, and using silence as a scare,” Tuason explains. “From [Steven] Soderbergh’s Kimi, I got the idea of noise-cancelling headphones.”

He continues, “undertone is two aural planes, the headphone plane and the haunted house plane, and then they combine in the end.”

Predominantly shot in a spooky home in Rexdale—a neighbourhood northwest of downtown Toronto—Tuason also embraced the long tradition of films that extract maximum tension from a single location.

“I spent my first round of research just watching all the one-location films,” Tuason notes. “Locke was one of them, as well as The Guilty, Pontypool, which is also Canadian, and even Reservoir Dogs.”

Yet for all its sonic experimentation and contained setting, undertone remains a visually immersive experience—one that treats its limitations as a creative catalyst rather than a constraint.

“When you have a restriction, like you have to stay in one location, I think people tend to be more creative—they have to find solutions to solve that problem,” Tuason softly explains. “I drew on many cinematic techniques to fill up that space with language, whether it was a tableau or cutting to different parts of the house when we hear banging… I felt like the threat could come from any room, and then it’s like the video game, Five Nights at Freddy’s.”

Now chuckling, Tuason reflects, “I really did have to go through an arsenal of techniques!”

Those limitations also shaped the performances. Unlike many horror films, the actors couldn’t lean heavily on exposition to explain what audiences were experiencing.

DiMarco’s largely off-screen, voice-driven performance especially played into the film’s stripped-down approach.

“Sometimes I borrowed inside jokes and references from real-life friendships and dynamics,” DiMarco explains. “My friends and I do a bit in FaceTime where we call each other and say ‘hellooooo’ like eight times before we start talking, so that was something we implemented as well—it’s a quick way to establish a history there, instantly.”

Kiri likewise embraced the film’s restrained tone, avoiding exaggerated reactions in favour of something more grounded.

“There’s a stillness to the movie that’s so powerful,” Kiri notes. “It felt cheap to do more than what I needed to do.”

That careful synthesis between the film’s sonic design, visual language, and performances feeds directly into its deeper themes—particularly its exploration of maternal guilt, neglect, and the lingering shadows of Catholic iconography.

For Tuason, those elements stem from personal experience.

“It definitely stemmed from my upbringing—Catholic—where there was a lot of iconography in the house I grew up in,” Tuason says.

He continues, “like the portraits of Mary and Jesus, and how your perspective of these images can be flipped based on your state of mind.”

He explains, “They could be images of comfort, but if you have unsolved trauma or repressed feelings of guilt or shame, now these portraits of Jesus looking at you could be him judging you instead of him protecting you.”

He adds, “It’s like a flip, a reversal, a mirror—like in the original Ghostbusters, a safe thought leads to the Marshmallow Man destroying the city.”

DiMarco agrees. “I feel like I’m still picking up on different themes every time I watch it… it taps into deep-rooted fears, like losing a parent… It’s a very claustrophobic film.”

Kiri adds, “You can pick one theme, and it turns into a kaleidoscope of different things… It’s why this movie had such a great response, it comes from such a true place, and from each of those themes, there are so many things that people can connect to in a stronger sense.”

Therein lies undertone’s quiet magic trick. By withholding as much as it reveals, the film invites audiences to fill its lingering silences with their own anxieties and fears. The result is a horror film that feels both intimate and cosmic—one that finds terror not in what appears on screen, but in what echoes around it.

undertone releases Friday, March 13.