NEW YORK (NYT NEWS SERVICE ).- There’s a lot meant to freak out audiences in “The Grudge,” the horror reboot that opened Jan. 3. One of them is the sound of peacocks.

The birds don’t appear in the film, but their startling squawks can be heard, in digitally altered form.

“They’re beautiful, but the way they sound is pretty unsettling,” said Taylor Newton Stewart, 41, one half of the composing duo behind the film’s soundtrack. “It sounds like a cry for help.”

Since 2014, Stewart and Andy Grush, who call themselves the Newton Brothers, though they are not related, have specialized in music in the key of fear. Their compositions have accompanied and augmented the terror of demonic possession (“Ouija: Origin of Evil”), crazed killers (“See No Evil 2,” “Hush”), childhood trauma (“Oculus,” “Gerald’s Game”) and all manner of ghastly apparitions (“Before I Wake,” “The Bye Bye Man”). Their last soundtrack, for “Doctor Sleep,” was like an aural haunted house: pounding heartbeats, creaking doors, ominous chants and a low dirty drone that suggested evil lurking behind every door.

When they started collaborating in 2011, they didn’t plan on their composing careers revolving around the stuff of nightmares. And the work, they’ll freely admit, can exert a psychological toll. “Being in a dark room staring at dark imagery for a long time, it does get to you,” Stewart said in a joint phone interview. “Sometimes you need to step aside and go watch ‘Finding Nemo’ with your niece.”

In the aughts, Stewart and Grush, 45, mainly worked, separately and sometimes uncredited, on other composers’ scores: Grush, a self-professed “classical music nerd” and pianist, was as an orchestrator; Stewart, the son of an opera singer, a synthesizer programmer. Meeting through mutual friends, they decided to forge their own composing careers, figuring they could cover more musical ground that way. Sure enough, as a duo, they moved adroitly through scoring projects, from tense political drama to action thriller to college sex comedy.

But even though they remain open to working in any genre, after the success of “Oculus” (2014), directed by Mike Flanagan, they were pegged as maestros of menace. They became Flanagan’s composers of choice, too, having scored six of his horror films so far, including “Doctor Sleep,” as well as the Netflix series he created, “The Haunting of Hill House.”

“Andy and Taylor understand the role of music in a film on a profound and instinctual level,” Flanagan said in an email. “They see beyond the score, and see the film itself as a symphony, and then refine their score so that it fits in harmony with all of the other elements. They create elaborate, terrifying and even gorgeous music. And they have never once repeated themselves.”

For the composers, scoring for horror is a license to get weird. They dabble in everything, including 12-tone and microtonal music — music that lives in the uncomfortable cracks between the more familiar musical notes — and punch-the-air alt-rock. (The end credits of “The Grudge” are set to “We Get What We Deserve,” all blistering guitars and hell-raising vocals, a collaboration with the Los Angeles grunge rock band Dead Sara.) In a single soundtrack, their lush orchestral pieces mingle with more deranged impressionistic soundscapes.

“I don’t think any other kind of film would give us the same sort of leeway to explore all the things we’re allowed to explore,” Grush said.

They are keen investigators of exotic and unconventional instruments, too. For “Ouija,” they employed the waterphone, whose otherworldly shimmer was also used to sinister effect in “The Exorcist.” For “Doctor Sleep,” they sought out a nearly 100-foot tall Aeolian harp, an instrument performed by the wind rather than a human player, while the persistent drone in that soundtrack was supplied by the Hurdy Grande, a bulky contraption invented by experimental composer Paul Dresher.

As with the peacocks, some of their most compelling sonic textures are derived from noninstruments. Scores have involved the sounds of bees, flies and hummingbirds, the bleat of a foghorn and the hum of an air-conditioning unit. “I’ll take a mallet and hit a microwave door for inspiration,” Grush said. “You just start making noise and wait to hear what happens.”

Back in the studio, these found sounds undergo merciless surgery through Soundtoys and other audio software: slowed down, stretched, warped, chopped up and digitally mutilated beyond recognition.

“It’s about trying to come up with something that you’ve never heard before,” Stewart said. “Not knowing what it is makes it scary. It’s like when you’re a child and you hear some weird sound, and your mind starts to think something’s out there. It’s the combination of the unknown factor and your mind wandering to what it could be, trying to explain the anomaly.”

As a listening experience, “it’s not going to work as a concert piece,” Grush said. “But it does serve the film.”

There are tried and tested horror film music tropes too, of course. Shrieking violins suggest some fast-approaching threat, while bow sticks striking their strings evoke fraying nerves or an inundation of tiny insects; and chaotic percussion simulate the protagonist’s heart-racing panic. The Newton Brothers use familiar techniques like these sparingly, tactically.

“If you’re making a scary scraping sound, you shouldn’t make that same scraping sound for a while. Even something uncomfortable becomes comfortable when you expect it,” Grush said. “So we’re constantly changing the sounds, the tempo, the rhythm of things so you can’t get too comfortable with anything.”

Silence and space are important, too. A slow-creeping melody or an unresolved chord progression is a surefire way to leave an audience on edge. “Scary or emotional moments are more effective when there’s a bit of a pause and a moment to breathe,” Stewart said. “Too much music lessens the impact when a big moment finally comes. And a moment of silence beforehand can let you really scare the bejesus out of somebody.”

But a truly effective horror score also includes musical moments that express a character’s vulnerability. It’s not just the stabbing shower-scene violins that made Bernard Herrman’s “Psycho” score effective, but the way their churning strains revealed the anxieties of Janet Leigh’s character early on. The horror is most horrifying when the audience is invested in the human drama.

“A good horror film, just like any good film, sucks you in, gets you involved with the characters in the story, the stakes,” Stewart said. “The music can really help in that aspect.”

Grush added, “The more that people care for a character, the more frightful or tragic it is when things start to happen to them.”

For the composers, these moments are also a welcome opportunity to indulge in their more melodious side. Their score for “The Haunting of Hill House,” for example, is driven by delicate, emoting piano, befitting the family drama at the center of the scares. It’s the kind of soundtrack, Grush said, you could listen to with your morning coffee.

“Until the bits that make you spill it.”

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