If your still short of Raspberry Pi’s, here’s a guy with several music projects, using small processors, mostly the ESP32. (The Daisy mentioned below)
Synthesizer library (organ) on 6 different platforms:
Pi Pico XIAO DaisySeed ESP32 ESP8266 Teensy4.1
Github Code
Arduino polyphonic synthesizer project (not a Moog) for ESP32 - STM32 - Teensy and more
ml_synth_pwm_osc_example (Update)
Perhaps a bit early Casio sounding, he is getting a lot pf polophony from little boards.
His 24 Github posts