Music box is a device that plays music when the handle is cranked. The only music boxes that appear in the series is during the movie Dragon Ball Z: Wrath of the Dragon.
After the end of the Hirudegarn war, a Konatsian Wizard sealed the warrior brothers Tapion and Minotia inside of specially designed music boxes and launched them into the far reaches of space in order to keep them out of reach of the evil Kashvar. Although the Kashvar wizard, Hoi, managed to free Minotia from his music box pretty easily, and had him killed as a result, Tapion's music box was more difficult to him to break its seal, requiring him to trick the Z Fighters to use the Dragon Balls. Tapion is released from his music box by use of the Dragon Balls, which in turn shatters it.
Later, after hearing Tapion's story, Bulma decides to create a room based on the broken music box design and the music the Hero's Flute produces so that Tapion can finally rest. Unfortunately, it failed to do so, almost releasing Hirudegarn.