This was composed in Schism Tracker, which is an exact clone of Impulse Tracker except it doesn't require DOS to run. That's the software used to create music for Unreal Engine 1 games like Unreal Tournament and Deus Ex. It's pretty much a grid that you arrange a bunch of little audio samples at different pitches onto to make a song. The only effects available are pitch slides and adjusting volume or panning. There's no delay, reverb, or any other complex effects we take for granted these days, but you can brute-force those things. For example, when I wanted an instrument to have reverb, I recorded the sample with reverb on it. When I wanted stereo delay, I just retriggered the notes at lower volumes on channels that were panned left and right. Trackers are also really good for composing noodley solos, so there's a bunch of those toward the end.

If you'd like to see the tracker in action, I posted a vid here: https://twitter.com/Fantishow/status/1374496589914329093?s=20