The "Earth God's Lyric" must be played in front of Medli in order to awaken her as the Sage of Earth.[3][4] Medli, with the help of Link, plays this song on her harp to open the entrance to the Earth Temple.[5]
This melody must be played numerous times inside the Earth Temple in order to break down several Stone Tablets and thus be able to progress through the dungeon. After defeating Jalhalla, Link conducts the Earth God's Lyric for Medli and Laruto so that the power to repel evil is restored to the Master Sword.
The following section is not part of the Zelda canon and should not be taken as such.
Hyrule Warriors
Medli plays the "Earth God's Lyric" on her Rito Harp in Hyrule Warriors. She plays this Song to create a Crest of Din on the ground as one of her attack combos and as one of her attacks while under the effects of Focus Spirit and it ends. She also plays the Song during her victory animation.
Trivia
The "Earth God's Lyric" is the first part of The Wind Waker introduction theme.
The Stone Tablet that teaches Link the "Earth God's Lyric" from The Wind Waker
References
↑Encyclopedia, Dark Horse Books, pg. 97 (TWWThe Wind Waker)
↑He attacked this temple and stole my soul, knowing that he had to remove the power contained in that enchanted blade. — Laruto (The Wind Waker)
↑The song you just conducted is one which will open the eyes of the new sage and awaken within that sage the melody that will carry our prayers to the gods. — Laruto (The Wind Waker)
↑Thanks to you, I've been awakened to the knowledge that I'm a sage of the Earth Temple. — Medli (The Wind Waker)
↑The door that blocks your way will only open when the sage plays that song. — Laruto (The Wind Waker)