When the Walt Disney company released their iconic movie Fantasia in 1940, it was the first feature film to have stereophonic sound–the film included a right, center, and left channel. In fact, the concept was so new to the general public that Disney eschewed any technical nomenclature and simply called the audio experience “Fantasound” to link the experience to the name of the film.

What’s just as interesting (if not even more interesting) than the bit of trivia about Disney being first in line with stereo sound is how they recorded the score. Rather than record the score in a Disney sound studio, almost the entire film score was recorded in the Academy of Music concert hall in Philadelphia, performed by the Philadelphia Orchestra, and recorded by an army of sound engineers—seen in the photo here—working out of the basement where 33 microphones across eight channels of audio were piped down to recording stations. The entire process took seven weeks, used over ninety miles of film to record the audio, and had to be completed in carefully controlled shifts to ensure the safety of the engineers and the performers—old film was nitrocellulose-based and only a certain number of film cans were allowed into the wooden building at any given time to avoid the risk of fire or explosion.