Eternity ~Memories of Waves and Light~ Music From Final Fantasy X-2 (久遠 ~光と波の記憶~ Music from FINAL FANTASY X-2, Kuon ~Hikari to Nami no Kioku~ Music from FINAL FANTASY X-2?) is a small promotional single of themes from Final Fantasy X-2. While the tracks share the same names as the ones on the OST, they are arranged differently. For example, the first track on this album used live instruments (piano, guitar, and bass) going along with the standard background music, whereas the game version uses more synthesizers.
The titular track was given in-game in the North American version of Final Fantasy X-2 as "KUON: Memories of Waves and Light".