Toronto soundtrack composer Mark Korven called up his friend Tony Duggan-Smith a year ago and asked the guitar maker to build an instrument specifically for horror films. Duggan-Smith, always up for an adventure, took a stab at it. The result is something they call the Apprehension Engine, and it is rather insane.

"The mission was to make something that causes people to feel strange and uncomfortable," Duggan-Smith says. "With a guitar, I'm trying to make a beautiful instrument with the sweetest, most pleasing sound possible. With the Apprehension Engine, we're trying to annoy people."

Duggan-Smith and Korven spoke with The Globe and Mail in Korven's basement in the Upper Beaches. The room is full of computers, acoustic instruments, keyboards and effect pedals, but on the coffee table sits a diabolical box of analog strange. And while it's roughly the size of a harmonium, the thing makes some of the most inharmonious screeches, drones and scratches you'll ever want to hear.

Story continues below advertisement

Or don't want to hear.

"It's a matter of personal perspective," Korven says. "Some people tell us the Apprehension Engine freaks them out, while others tell us the sounds are beautiful and relaxing."

The handmade instrument was inspired by something called the Soundtrack Box, invented by the Oslo-based new-music technologist Koka Nikoladze. The much larger Apprehension Engine – called the "nightmare machine" in a recent CNN piece on the device – has a couple of necks with strings and tuning pegs. A wooden hand-cranked wheel produces drone effects, and metal rulers and clock springs can be bowed for screeching sounds. There's a magnet with a small box of metal junk underneath for scratches and clicks. A battery-powered electromagnetic EBow device (used by guitarists for a sound-stretching effect) is employed for sustaining notes and thwanging metal rods round out the weird.

"We're not trying to play melodies with this," says Korven, while demonstrating the instrument's oddball capabilities. As Korven manipulates the thing, the room's temperature drops about 10 degrees and the composer's tiny dog retreats to an upstairs closet.

Korven, who would normally use digital samples for eerie effects, is best known for the unsettling score to Robert Eggers's 2015 horror film The Witch, a movie frightening enough to leave Stephen King calling for mommy. Duggan-Smith is a well established Canadian luthier. He was one of the seven crafts people commissioned by the McMichael Gallery for its current Group of Seven Guitar Project.

The apparatus took only a couple of weeks to build. "It was a liberating process," Duggan-Smith says. "When you're making high-end guitars, so much of the thought is going into the aesthetics. But with this, there was zero time for that."

Originally envisioned as a one-off commission, plans now call for the building of 10 new devices that will be based on the prototype, with refinements.

Story continues below advertisement

But 10 new for who? Who needs such a thing? According to Korven and Duggan-Smith, inquiries into the instrument (which has its own website, apprehensionengine.com) have come from musicians, mixed-media artists and major composers.

"I'm surprised that people want to own them," Korven says. "Every third person who contacts us asks where they can get one."

In another surprising development, what was initially developed for scoring will now be used for live performances. Someone from a Venice Beach freak show contacted the inventors, as did an Australian university, for possible use in the Sydney Opera House.

Closer to home, the Apprehension Engine will make its live debut at the Guelph Jazz Festival on Sept. 16. Expect a little stage fright, then, on the stage and in the audience, too.