How does custom melody music box work?

Custom melody music box works by inserting a perforated paper strip and cranking the handle.

The paper strip has little punched holes which represent notes. When these little holes reach the music box mechanism, it flicks a particular string. If you keep cranking the handle, you will hear a melody. 

Tip: in case the strip is not traveling while you crank the handle, you need to push the strip further for mechanism to catch it.