Long before the days of WinAmp visualisers, the oscilloscope was making sound visible in green on black glory. Few have really pushed the potential of this rudimentary little device. But this is what happens when you make music from sounds that already produce recognisable visuals.
YouTuber Techmoan refurbished a really prime specimen from the oscilloscope world — the Tektronix 760A. Then he set it up to play Jerobeam Fenderson's Oscilloscope Music, a selection of tracks that are built from sounds that produce distinct images.
Fenderson has a decent FAQ on their website for those who want to tinker with this kind of thing. Basically, you'll need to be able output left and right channels from an audio interface into an oscilloscope that can operate in X/Y mode, AKA lissajous mode. There are various ways to approach it, such as using OsciStudio for Blender (free) which converts 3D objects into sound files. Then, take those sound files and start mixing them into music with your favourite audio program.
For those who want to do it the old-fashioned way, here's what the maths looks like for drawing a butterfly:
Yeah, I don't know either.
For those who just want to play around with an oscilloscope at home, here's a downloadable emulator.