just wanted to +1 this.
what i’ve seen is stuff like bitscope, which is 1) a product family of high-speed acquisition circuits, and 2) an API for dumping the captured data by USB, controlling trace parameters, &c. (rpi being a potentially host choice if you want to DIY a self-contained unit with the bitscope-micro board - though again, you don’t need a lot of compute power for this.) it looks interesting - i too have no personal experience, curious to hear about it if others do.
if you’re just interested in visualizing audio waveforms then this is considered “low frequency” for a DSO, and you can find more options from searching for that, like this thing
but yea the pi doesn’t really have appropriate acquisition circuitry built in.
