Part of what makes this all work is I2S (Inter-IC Sound), a format for communicating PCM audio data between devices. Besides the ESP32, at the heart of it all is an SD card reader breakout board ...

Inside the neatly designed 3D printed box the hardware is quite straightforward, a WeMos ESP32 board and a MAX98357A I2S digital amplifier ... has code for both Arduino and Platform.io and is ...