Gage

Gage is a character in. He is a member of the Lokomo people and Guardian of the Forest Realm who resides in the Forest Sanctuary. Like the rest of the Lokomo, Gage possesses a sacred instrument, his being the cello, which generates energy to power the Spirit Tracks when played with another sacred instrument.

Biography
In order for Link to access the chamber in which Gage is located, he must first connect the two stone statues that are facing each other on a tablet outside of the Lokomo's room. Once he does so, the door will open, and give acces to the room where link can meet Gage. He mentions that he has heard about Link and Zelda's journey to restore the Spirit Tracks to the Forest Temple, and goes on to teach the young duo on how to recover the tracks by playing a Lokomo Song. A Lokomo Song, Gage explains, is a duet that requires two sacred instruments, in this case being Gage's cello and Link's Spirit Flute. Before performing the first Lokomo Song, Gage teaches Link on how to play the Spirit Flute, and after he is done explaining, the young hero and the Lokomo play the duet that restores the Spirit Tracks to the Forest Temple.

During the final battle against Malladus, Princess Zelda sings a duet with Link, and soon after this, all five of the Lokomos, including Gage, join in to form a full orchestrated version of the piece. This melody weakens Malladus and reveals a weak spot in his back, which is necessary to defeat the Demon King once and for all.

Gage is last seen during the ending credits when Anjean, along with the rest of the Lokomos, departs towards the heavens after the defeat of the Demon King since their protection no longer needed in the land of Hyrule.

Trivia

 * Gage's name is a play on the word "gauge", as in an engine's gauge.