“Yes, there were literally rats down there,” says Scott Burnham, who in the mid-’70s hunkered down in a basement in Kalamazoo, Mich., in search of a new sound for garage bands. At the time, Burnham worked as Hippie in Charge of Technology — his official title — for a manufacturer of electric-guitar cables and accessories called Pro Co Sound. While customers wandered around the company’s first-floor showroom, Burnham tinkered below. “I had started thinking about what would make a killer distortion pedal,” he says.

Distortion pedals have been around since the 1960s; they scramble the signal from an electrical instrument and make it sound “fuzzier.” This is what adds growl to the Rolling Stones’ “(I Can’t Get No) Satisfaction.” Burnham wanted to create a distortion pedal that would capture the essence of stadium rock — the buzz of an amp cranked to teeth-rattling decibels.

One day, as he was soldering parts to create a distortion machine, he picked up the wrong resistor and attached it to his circuit board. “Woooooo,” Burnham howled, imitating the sound that the rig made. “I thought, This is something I have never heard.” The shriek was far weirder than the fuzz effect he’d been trying to achieve, and he quickly built it into a pedal he named the Rat.