A Contest of Aeons

"A Contest of Aeons" (召喚獣バトル) also known as, "Summoned Beast Battle" is the boss theme that plays during the final battle sequence against Yuna's Aeons which have been possessed by Yu Yevon in Final Fantasy X. In the International and PAL versions, this track also plays when the player encounters Penance.

This track is composed by Junya Nakano. It is the seventeenth track on disc 4 of the game's original soundtrack. The song begins with the melody of the Hymn of the Fayth, then an original part is led by the harp. The final section contains the motive of "Enemy Attack", the generic boss theme by the same composer.

Final Fantasy Fables: Chocobo's Dungeon
This track is used as a battle theme in this game, renamed "Alexander Battle". Rearranged for the game by Yuzo Takahashi, it was released in the game's soundtrack in 2008 as the twenty-fifth track.

Dissidia 012 Final Fantasy
An arrangement of this battle theme by Takeharu Ishimoto appears as the 42nd track of Disc 1 in the original soundtrack. It acts as final boss theme for duel between Yuna and the Emperor. It is entitled "Summoned Beast Battle".

Theatrhythm Final Fantasy
This track is used in Theatrhythm Final Fantasy as one of the songs available as downloadable content.

Dragon Quest & Final Fantasy in Itadaki Street Portable
An arrangement of "A Contest of Aeons" is included in this crossover between Final Fantasy and Dragon Quest for the PlayStation Portable. It is very similar to its original version, but its development was remixed.