As any Doom player knows, a good chunk of the visceral joy and laser-like focus that arise while ripping and tearing your way through demons is due to the game's heavy soundtrack. Through some dark alchemy, it thumps and chugs and chings at all the right moments, making every weighty punch feel like a cannon shot.
The end result is amazing, but seeing how the music was made is truly something else. Two weeks ago, in a talk at the 2017 Game Developers Conference in San Francisco, game composer Mick Gordon walked us mere mortals through his process. I have never seen anything like the silly business on display.
The most interesting revelation, to me, is that the game's signature sound—pulsing, distorted synth lines that roar and squeal like the devil—is really nothing more than a simple sine wave. This is the most basic form of synthesis, and it kind of sounds like nothing; it's just a boring, smooth, rounded bass tone. Gordon took sine wave patterns and turned them into the diesel-choked riffs we all know and love by running them through a massive array of effects that he thinks of as an instrument on its own.
The way it works is this: A single sine wave is split into four signals and sent down four effects chains. Two of these contain no fewer than four distortion and phaser pedals, to create harmonics. The third chain is pretty much for echo and reverb, and the final chain overloaded a tiny amp mic'd up for feedback. Put it all together and compress the ever-loving shit out of it—this basically makes louder sounds quieter and brings smaller sounds up in the overall mix, key for the music's swelling screeches—and you've got Doom, baby.
Algorithms were also involved in creating the game's memorable guitar tones, which sound more like roaring chainsaws than any third-rate metal band. Well, as it turns out, this is because guitar riffs were "morphed" together with the sound of the chainsaw from the original 90s Doom. This was accomplished with a plug-in called MORPH. How MORPH works is a bit of a mystery, but it was originally designed by the now-defunct Prosoniq, which made a name for itself by using neural networks in music production.
One possibility, floated by machine learning expert Alex Champandard on Twitter, is that MORPH uses a neural network technique called "style transfer," which is currently a darling of the field and is finding use in everything from apps that make selfies look like works of art to projects that re-imagine famous movies as impressionistic animations.
Now, go forth and slay some demons with a new appreciation for how metal—nay, more metal than metal—the Doom soundtrack really is.
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