4-voice Arduino Synthesizer from 4 output pins producing squarewaves combined into one output using NOR Gate and Mixer circuitry.
Programed to use the Arduino tone() function and routines that toggle the pin outputs at multiples of the main program loop() speed.
One program uses pots to control 4 voice frequencies. Another uses MIDI Input to record and playback 3 polyphonic voices.
Includes a unique analog Fuzz box circuit on one of the voices that uses an Arduino output to enhance the distortion.