You control it like most drum computers: you draw the beats on a pattern of sixteen dots, perfectly suited for generic 4/4 rhythms.
There are 8 lines, each controlling 1 servo motor.
Most of the servos have a percussion item both on the left and the right, thatâ€™s why the pattern buttons have 3 states: off, left, right.
That makes 14 distinct percussion sounds for the drummerbot.
The pattern in the webbrowser is packed into a string, which get send to the Arduino via HTTP.
You can use a wifi module and a http server on the Arduino, or you can use another device attached to the Arduino through a COM port.
The Arduino receives the string, unpacks it back to a pattern and simple loops over the steps controlling each servo.
The Arduino code can be got from here. The music did make me smile!