The first design is a copy of the music box and is fitted into an interactive interface. The user can click on the metal tube and mark the notes. When the notes play, the metal bars will also move. This would be considered a playback system.
The second design is based on a real instrument called the xylophone. The user can tap on each metal bar and play the melody. This would be considered a real-time interactive system. Similarly, the third design interacts based on user movement and can play different frequencies/notes at a different position on the x and y-axis.