Earlier quoted context omitted.
If you don't count your time whatsoever and don't go for the nice case design. I mean at the extreme case, if you can tolerate 40ms of latency and stuttering, a Raspberry Pi and some USB soundcards can do it all. The actual power needed is reasonable and ADC/DACs aren't that insane. A Teensy 4.1 connected to an ESP32 could probably do most of this, if you wanted to do $15k of software development in your spare time a…
Interestingly enough, it seems like the KORG wavestate is actually based on some Raspberry Pi, according to KORG's github page, so you can definitely get less than 40ms latency and no stutter. And yeah, Teensy or even FPGA evaluation boards can get you very far, since software development in your spare time is "free". If you search the web, you'll find many examples of such projects. For example I remember some FPGA…
Or maybe they just have some good IO. It doesn't seem to be CPU limited exactly, it's just the built in sound device doesn't like it if you turn down the block size too much. USB cards are a bit happier.