It was composed by Yasunori Mitsuda and contains 44 tracks, including a Bulgarian choral song and two pieces performed by the Irish singer Joanne Hogg.

The soundtrack was composed with strong traditional and Irish music influences, while the lyrics for the vocal tracks were written by the game's director Tetsuya Takahashi and its scenario writer Masato Kato.

The composer, along with Joanne Hogg, reprised their roles for the soundtrack to Xenogears's spiritual prequel Xenosaga Episode I: Der Wille zur Macht in 2002.

[3] Mitsuda considered it hard at times to maintain his motivation throughout the whole two-year period, especially since he had to wait for the end to see the most dramatic tracks implemented.

Mitsuda initially had difficulties finding an artist that matched his vision,[5] but eventually chose Joanne Hogg from the Celtic band Iona after stumbling upon their album The Book of Kells in a CD store and listening to the song "Chi-Rho".

[11] Mitsuda felt that composing for the game was very difficult due to the unfamiliarity of most Japanese with foreign traditionals, but expressed his wish for listeners of the soundtrack to open up to music from all over the world.

[7] The opening movie of the game was produced before the corresponding track "Dark Dawn" was, and Mitsuda had to rearrange his composition after realizing some parts were out of synch with the frames by about a minute and a half.

[14] The choral track, titled "The Beginning and the End", was performed by a 41-voice choir named The Great Voices of Bulgaria and features lyrics written by Tetsuya Takahashi.

[10] The instrumental tracks of the score were programmed with the PlayStation sound module in Tokyo, Japan, while "The Beginning and the End" was recorded live in Sofia, Bulgaria.

[4][7] When Titanic premiered in November 1997, Mitsuda noticed coincidental similarities between the film's ending song, Celine Dion's "My Heart Will Go On", and the Irish-themed music he was composing for Xenogears.

[1] As with some of his previous soundtracks, Mitsuda would stay in the Japanese studio for long amounts of time and regularly fall asleep from overwork, while some melodies would first come to him in his dreams, such as that of "Ties of Sea and Flames".

[10] Critics also noticed similarities between some melodies and Mitsuda's previous work Chrono Trigger, though reviewers felt that those of Xenogears were more "widely based" and had a distinctive Celtic sound.

[10][24] The final boss theme "The One Who Bares Fangs at God" received the most diverse comments, ranging from praises[21][22] to criticism, due to its reliance on synth choral sound effects rather than a clear melody.

[31] In 2002, Mitsuda composed the score to Monolith Soft's Xenosaga Episode I: Der Wille zur Macht, the spiritual prequel to Xenogears, also directed by Tetsuya Takahashi.

[34] The album features 20 tracks arranged from the Xenogears score and performed with acoustic instruments, such as piano, flute, guitar and violin.