I own a Korg MS-20 Mini, and have been using it to learn a bit more about music and signal generation. It has configurable oscilators, envelopes, and filters. The primary way we interact with sound is with our ears, but electronic tools can also be made to “hear” and then display that information visually. I’ve built an LED display (on top of the synth) to visualize the intensity of each of 7 bands of our audible spectrum.