When children press a key on the piano, they not only hear a sound, they see a ball pop up! The clear arch guides the popped balls onto a different pipe so when another note is played, they'll pop some more! Flip the switch to go from piano tones to hearing fun sound effects when the keys are pressed. Adults can remove the arch to allow the 1-1/4 inch balls to land and roll on the floor, encouraging children to crawl after them. Develops: Cognitive Learning, Understanding the cause effect relationship, Sensory Development, Exploring with hands and eyes, experiencing bright colors and sounds, Exploring self-expression through musical play. Requires 3 AA batteries (included).