Elegy of Emptiness

The "Elegy of Emptiness" is a song featured in Majora's Mask.

Learning Location
Played on the Ocarina of Time, it is taught by the King of Ikana in Ikana Castle after Link defeats him.

Uses
The "Elegy of Emptiness" leaves an exact replica of the form Link is in at the time, but it can only make one of each at a time. It is required to scale up the Stone Tower, and it's also necessary to solve several puzzles inside the Stone Tower Temple.

A total of four replicas can exist at any given time, one for each of Link's forms. They all play a pivotal role, but the Deku form is the least used, as it is far too light in most cases, while the Goron replica is specifically used to press down switches that are bigger than usual. It is important to note that the replicas can only be formed if Link is in any of the areas pertaining to Ikana Canyon, for if the song is played anywhere else, it won't have any effect.

The statues may block certain projectiles such as Octorock rocks.

The replicas that Link's Deku, Goron, and Zora form leave are that of Deku Butler's Son, Darmani, and Mikau, respectively.

Etymology
An elegy is a mournful, melancholic or plaintive poem, especially a funeral song or a lament for the dead.

Trivia

 * The human Link statue's face is believed by many to be based off of Shigeru Miyamoto's face.
 * The Deku statue is useless in the Stone Tower Temple because it is unable to press switches because of its light weight.
 * The Deku Statue is believed to be the appearance of the Deku Butler's son when he was alive.