“There was something I didn’t tell anyone else that day. That song we heard there, in the temple…I knew it from my childhood. It was proof that Spira and Zanarkand were connected somehow. At least to me it was.”
The “Hymn of the Fayth” (祈りの歌, Inori no Uta?, lit. “Song of Prayer”) is a song composed by Masashi Hamauzu and Nobuo Uematsu, featuring lyrics by scenario writer Kazushige Nojima, for Final Fantasy X.
Composed in Dorian mode, it consists of a single melodic line reminiscent of Gregorian chant. In the game, the hymn serves as a transitional song and an indicator of religious importance or solemnity, though its lyrics don’t appear to have any meaning to the game’s characters.
The “Hymn of the Fayth” was originally a Zanarkand song sung in defiance of Bevelle in the Machina War 1000 years previous to game events. Yevon took the song and made it scripture, spreading it around saying it was a holy song of Yevon sung to soothe the souls of the dead.
The song represents an additional mystery in that both Tidus and Jecht know the tune, a hymn glorifying Yevon and the fayth, while knowledge of these things did not exist in their home Zanarkand. As both Tidus and Jecht, as well as their world, are dreams of the fayth, they might have gained knowledge of the tune subconsciously; the fayth that seems personally linked to Tidus, Bahamut, sings the song on at least one occasion.
Another theory is that, considering the song was around before the war, and the original inhabitants of Dream Zanarkand were created from the memories of the fayth, the hymn might have been passed down in Dream Zanarkand, much as the prayer of Thanksgiving is passed down with its original meaning of victory.
The Hymn was used to weaken Sin late in the game so that the party could attack head on using the airship. Shelinda was instructed to tell all of Spira to listen for a singing ship in the sky, and the people were to sing along.