Song of Time
Princess Zelda teaches Link the Song of Time after he has obtained all three Spiritual Stones and then as soon as Link approaches Hyrule Castle. Zelda and Impa will be seen fleeing the castle being pursued by Ganondorf. She will throw the Ocarina of Time into the moat and Link will go into a type of dream world when he picks it up.
The Song of Time can be used to open the Door of Time and to move large blue stones found throughout the game.