We can use Arduino to make many interactive works. The most commonly used one is acoustic-optic display. All the previous experiment has something to do with LED. However, the circuit in this experiment can produce sound. Normally, the experiment is done with a buzzer but not a speaker while buzzer is more simpler and easier to use. The buzzer we introduced here is a passive buzzer. It cannot be actuated by itself, but by external pulse frequencies. Different frequency produces different sound. We can use Arduino to code the melody of a song, which is quite fun and simple.