Fuse

Fuse is Disc 1, Track 14 on the Xenogears Original Soundtrack and track 15 on the Xenogears Original Soundtrack Revival Disc -the first and the last-. The track was remixed together with Grahf, Ruler of Darkness for the Xenogears 20th Anniversary Concert -The Beginning and the End- as Grahf, Ruler of Darkness - Fuse, and is the 7th track on the associated Blu-Ray disc.

It plays as the battle music against Solaris' Mobile Surface Supremacy Weapon, as well as in the immediately prior and subsequent cutscenes, and against. It also plays as the music in the following cutscenes:
 * Enemy Gears notice Fei wandering in the Aveh desert, and attack.
 * The Aveh sand cruiser begins sinking after being attacked by Bart and his crew. (The music continues as the area theme until Fei and Citan escape.
 * Shakhan's troops surround Bart and the party during his attempted invasion of Bledavik.
 * Ramsus's forces attack the Yggdrasil as it attempts to escape Bledavik.
 * Ramsus unsuccessfully attempts to fight Id when he shows up in the Aveh desert.
 * The freight train that Fei and Citan are riding on in Nortune begins to come apart.
 * The party notices Primera being harassed on the deck of the Thames.
 * Billy waits for his Gear Renmazuo after being noticed by the Giant Wels.
 * The party arrives at the Ethos Headquarters and sees that it has been attacked. (The music continues as the area theme and the battle theme until the party leaves the Ethos HQ.)
 * Wels from the Ezekiel descend upon the Thames.
 * Seraphita and Tolone retreat in Zeboim. (The music continues as the area theme until the party leaves Zeboim, although the interim cutscenes have different music.)
 * Margie enters Andvari in the Nisan Mausoleum.
 * Shakhan dies after the party defeats him at the Ignas Gate.
 * Fei and Elly are discovered in Solaris. (The music continues as the area theme and the battle theme until they arrive at Elly's house.)
 * Elly's father notices Elly attempting to discover the whereabouts of the rest of the party.
 * The party is reunited, including Elly's mother and father, after the Solaris gate is destroyed. (The music continues as the area theme until the next cutscene.)
 * Id destroys Etrenank.
 * A Shevat emissary notifies Fei and Elly that Solaris' mobile weapons are approaching Shevat.
 * The attack on Merkava induces a secondary explosion.