Elegy of Emptiness
The song, when played, leaves a statue behind where Link was standing, which can be used to hold switches down. One statue can be used for each form (Deku Scrub, Zora, Goron, Hylian), which means up to four statues can be out at once. Some switches are bigger, however, and the Goron statue must be used for these switches. The Deku Link statue is far too light for most switches, so it isn't used as much.
The Elegy of Emptiness is used to get into Stone Tower Temple, as well as to solve many puzzles inside.
How to Play it
To play it, play the following notes on the C-Buttons: → ← → ↓ → ↑ ←. In order to play it in real life, the notes are A B A F A D B.