Assuming your "modules" are discrete components and some op amp ICs, audio circuits (things that generate or modify waveforms) are really good for building intu

Assuming your "modules" are discrete components and some op amp ICs, audio circuits (things that generate or modify waveforms) are really good for building intuition: - Relevant frequencies are low enough so you can breadboard circuits, use cheap components etc. - You can hear what everything is doing, so it's intuitive and you don't need test equipment - There are plenty of tutorials, because musicians have been doing this crap for decades For example, you can build a simple "wah-wah pedal" or low pass/high pass filters, swap in different components, and hear what happens.