For the technical details, it's built around a Sipeed Longan Nano microcontroller module, connected up to a small amplifier, some little pill box speakers, and a bunch of microswitches. The microcontroller itself is a GD32VF103, a weird Chinese creation of dubious legality that stuffs a RISC-V core into a clone of an STM32F103 to replace the original ARM core.
It's pretty fast, and can run the built-in tiny LCD at 60 FPS along with 10 voices of Karplus-Strong synthesis.
@WAHa_06x36 this algorithm makes no sense and yet it appears to produce pretty good results
-F