After you receive the Fairy Ocarina from Saria, do the bottle glitch (you can learn this from other codes on this site) and change the Fairy Ocarina into a bottle, BEFORE MEETING WITH PRINCESS ZELDA. Then, head to the Castle and meet with Zelda. When Impa teaches you Zelda's Lullaby, you won't pull out the Fairy Ocarina--you'll pull out the Ocarina of Time!
Don't get too happy about this. After this event, you won't have the Ocarina of Time with you (I don't think, I forgot). And you won't have the Fairy Ocarina, either, so you should probably just erase that game after doing this glitch.
