Reminiscence (XS1)

 is Disc 1, Track 6 on the Xenosaga Original Soundtrack and Disc 2, Track 5 on the album. ('Reminiscence' is an unofficial translation, as seen in the VGMdb listing of the album.) Kokoro (and by extension Kokoro instrumental) are both remixes of this piece, and, Shion ~Memories of the Past~, and Shion ~Emotion~ are all based upon the melody at the start. Shion's Crisis also uses the melody at the start as a motif. Finally, the melody at the start of The Girl Who Closed Her Heart and is similar to that at the start of this piece.

It plays in the following cutscenes:
 * Shion and Kevin talk the night before KOS-MOS's planned awakening (flashback).
 * Shion reveals she was from Miltia in the Realian Maintenance Room on the Woglinde.
 * Shion and KOS-MOS reassure MOMO about her origins and Dr. Mizrahi in the Durandal's park.
 * Kevin tells Shion that KOS-MOS has been exhibiting emotional behaviour (flashback).
 * Allen and chaos talk about Shion's emotional reticence in the Durandal's park.