Can you build a playable synthesizer in a single afternoon?

video upload by Illegal State Of Mind

"Can you build a playable synthesizer in a single afternoon? Here's my attempt: a DIY synth built from a basic ESP32 I had lying around.

At its heart is a DCO: a digitally controlled oscillator. The waveform isn't generated in code. It comes straight from the PWM outputs, while the code only sets the pitch, pulse width and modulation. The result is a fat, raw, monophonic sound with accurate notes and no tuning headaches.

How this ESP32 synth works:
• Two PWM signals from GPIO 18 and 19
• A simple resistor mixer and a capacitor on the output
• MIDI input built around a 6N137 optocoupler, three resistors and a socket (powered from the ESP32 board)
• Pitch Bend and Modulation over MIDI
• Pulse width and detune of the second oscillator controlled by knobs

What this synthesizer doesn't have (yet): an envelope, polyphony and a filter. They can all be added later in the analog part of the signal path, and I'll start working on them soon."