This is not supposed to be used with existing code. The point of this project is to have a dedicated seperate "processor" for tone generation, as inefficient as that may be. You need one ATmega328p ...

CW-arduino Very simple Arduino Uno CW practice tone generator ...

The robot centers around an Arduino which manages to control a plethora of auxiliary boards. The alarm clock part of the build has a readout in the center of the robot’s chest.