I made this "action" gift for my granddaughter Alexandra when she was just 3 years old. Today (the 21st of November) she is 18 years old! A small and inexpensive electronic keyboard is the heart of the project. As the video shows I cut the piano into two pieces to get the mechanism to function as shown. The battery compartment and speaker are separated from the keyboard and other electronics. The keyboard is mounded with a kitchen cabinet hinge that has built-in spring action. This gives just the right amount of force to let the "fingers" activate the keys.
The keys of the piano are manipulated by short pieces of rubber hose (fingers) that I made from automobile vacuum line. The fingers are friction mounted in holes on a laminated plywood wheel that I rotate with a hand crank. I made the ratcheting mechanism from a toggle bolt - this keeps you from turning the crank in the wrong direction.
The wooden mouse is attached to the flat rubber belt with an old fashion thumb tack. I got the belt from an old computer or printer.
It was only when I was preparing this instructable that I realized I didn't put a tail on the mouse!