you'll need to reach friendship level 15 with My Melody, who is My Sweet Piano's best friend. Once you reach this friendship ...

Additionally, you'll need to meet My Sweet Piano. My Melody only has 20 friendship levels, so this requires you to get almost all the way to maximum friendship. After you've met these requirements ...

The piano and guitar can play both low and high pitch sounds. A melody is made up of a mixture of high and low pitch sounds played one after the other. It's easier to remember that melody is the tune.