Prelude of Light

The "Prelude of Light" is a song from The Legend of Zelda: Ocarina of Time. It transports Link to the Temple of Time whenever he plays the song on his Ocarina of Time, presumably because the Temple of Time is the means of reaching the Sacred Realm and, from there, the Temple of Light, although it is not possible to travel to this location in the game. The song is also used for the fourth howling stone in Twilight Princess.

Link can play the "Prelude of Light" on the Ocarina of Time by playing Up-C, Right-C, Up-C, Right-C, Left-C, Up-C. The actual pitches of the notes translate as follows: D, A, D, A, B, D.

Story
After completing the Forest Temple and awakening Saria as the Sage of Forest, Link returns to the Temple of Time and meets Sheik. The mysterious Sheikah tells him that the Master Sword and the Pedestal of Time function as a sort time travel device, with which Link can return to his childhood form of seven years prior. To aid him in returning to the Temple of Time more efficiently, Sheik teaches Link the "Prelude of Light".

Etymology
A prelude is a song that introduces another. Its name could be taken literally to mean "Introduction of Light".