The Apprehension Engine is a custom-made musical instrument designed to produce the scary, tension-building noises associated with horror movies, but without the all-too-obvious digital chopping and synthesizing invariably involved. The result is something organic and seamlessly natural—something that goes beyond fear and fright to nail you to some deep Jungian place so completely you become a part of it. And she says I'm hard to shop for!
Christopher Bickel at Dangerous Minds:
"The Apprehension Engine," as it is called, was created by Canadian guitar maker Tony Duggan-Smith as a "one off" for Mark Korven, who is best known for his soundtrack work on The VVitch.
Compare to the classic analogue horror instrument, the waterphone: