So I'm looking to replicate this sound with a DIY circuit. The sound I'm looking for is not the reverb, but the dry. It sounds like the popular eurorack module "rings". I believe this has something to do with resonance. I've looked into resonant circuits but I'm seriously swimming up stream. I don't know the correct search terms, or even if a resonant circuit actually produces sounds like this.
I created a resonant circuit here, where you can see and hear (a bit crude) the waveforms as things are changed. But this is using an AC sound source. I think this and many other circuits I've tried don't perform with DC sound sources.