Music Box

The Music Box is an item which first appears in Super Mario Bros. 3. Here, Music Boxes are a white square depicting a musical note, and it has a sand-colored pad on the top and a crank to the side. They somewhat resemble Jump Blocks.

Super Mario Bros. 3
In Super Mario Bros. 3, a Music Box is a common item that causes all Hammer Brother, Fire Brother, Boomerang Brother, and Sledge Brother Enemy Courses, as well as the Piranha Plant stages in Pipe Land, to fall asleep so that Mario and Luigi can sneak past them. After one clears a level and/or loses a life twice, they wake up again. The song that is played is a soothing version of the Super Mario Bros. Ground Theme. The pitch level of the music was adjusted for both Super Mario All-Stars and Super Mario Advance 4: Super Mario Bros. 3.

Nintendo Adventure Books
In the book Koopa Capers from the Nintendo Adventure Books series, Luigi tries to whistle the tune from the Music Box to escape the Sledge Brothers. While it does make them drowsy, they avoid falling asleep completely.

Wario Land 3
In Wario Land 3, their name is formatted as music boxes. Music boxes have a large role in the game, which is even set within an enigmatic music box with an entire world inside of it. Wario's journey is focused on the collection of five different music boxes, which, if all played, can free a hidden figure claiming to be the music box world's unjustly accursed leader, helps Wario through his quest. Wario, in the end, collects the five music boxes scattered around the larger one and frees the figure, only to discover that he is evil; Wario then defeats him and saves the music box, which he is permitted to leave.

WarioWare: Twisted!
In WarioWare: Twisted!, the music box makes a cameo in Wario's House.

Super Mario Bros. 3

 * Wii Virtual Console manual: "Use this item to make enemies on the map screen fall asleep temporarily."
 * 3DS Virtual Console manual: "Allows Mario to put the Hammer Bros. and other map-screen enemies to sleep."

Trivia

 * The tune was remixed in Mario Party 10 as the results music when a Bowser Party is finished.