Super Mario Stepper
There is neither a motor shield nor any "stepper-music" library used. Everything is done just by .step() function from Stepper.h (essential library of Arduino IDE). To achieve a polyphonic sound, two motors are used playing different notes each. The execution of the Arduino's code is synchronous. Therefore each motor is controlled by a separate board. When the program starts executing, it sets the HIGH level of the pin 14. The second Arduino is listening for this change and consequently they start at the same time.