This Instrument Provided The Sound Of 'Terror' In The Knock At The Cabin Score [Exclusive]

"Knock at the Cabin" is a tense film. M. Night Shyamalan's latest clocks in at a 100-minute runtime, and nearly every single one of those minutes arrives with the intention of holding our hearts in a vise grip of anxiety. Much of the movie's intensity comes from its cast, led by a phenomenal Dave Bautista, while the feature's thrills pull from a script based on Paul Tremblay's also-harrowing book.

But "Knock at the Cabin" succeeds as an apocalyptic psychological thriller thanks in large part to its filmmaking and design, including a knockout score by composer Herdís Stefánsdóttir. The musician has composed for projects like the Apple TV+ gothic series, "The Essex Serpent," and the short-lived graphic novel adaptation, "Y: The Last Man." "Knock at the Cabin," however, offered new opportunities for the composer to get creative. Stefánsdóttir spoke with /Film's Jack Giroux about what it was like working on the project, and along the way revealed that she made the movie's signature sound with an unlikely instrument.

Need an unnerving drone sound? Check out the contrabass clarinet

"There's one completely crazy instrument that I recorded," Herdís Stefánsdóttir told /Film. "I had never heard it played before. It's the contrabass clarinet." On the woodwind spectrum, contrabass clarinets are an octave lower than bass clarinets, and two octaves lower than traditional soprano clarinets. The composer points out that the unique instrument "goes so many octaves lower" than those you'd normally hear, and notes that its central to the theme that accompanies the four strangers who appear at the doorstep of the film's much put-upon central family.

"In the 'Four Horseman' cue, the bass drone you hear in the beginning is the contrabass clarinet, and it creates all these weird squeaks and noises and harmonics," Stefánsdóttir said. The track, which you can listen to on Back Lot Music's YouTube channel, starts with a buzzing noise that sounds a bit like a helicopter or the wings of an insect. Both images fit perfectly with the film's apocalyptic themes of potential "plagues" unleashed upon the modern world.

'It is terror, because it comes from your gut'

Herdís Stefánsdóttir also speaks to the deep unease the instrument inspires, saying, "For me, the sound drone of the contrabass clarinet, it is terror, because it comes from your gut. It's somewhere down there." The contrabass clarinet is uncommon but not unheard of, but the "Knock at the Cabin" score doesn't come together thanks to its strange tone alone. According to Stefánsdóttir, an Iceland-based American composer named John McCowen played the instrument for the film, and McCowen knows how to unlock some even more chill-inducing sounds from the contrabass clarinet.

"Because it's a woodwind instrument, it also has all these surprising, squeaky wood sounds. That became a fundamental source in the terror," Stefánsdóttir explained. She said that McCowen is "probably one of the handful of people in the world that knows how to play this instrument with these crazy extended techniques," adding that "it's a very unique way of playing the instrument."

The result is impressive: A low drone that activates audiences' fight-or-flight instincts from the moment they first meet the mysterious characters played by Dave Bautista, Rupert Grint, Abby Quinn, and Nikki Amuka-Bird. The movie never gives viewers a respite from the intensity of its strange but powerful central story, and Stefánsdóttir's music is the thrumming force that drives the tension home from the film's first moment to its last.