A Secret Volition

 is Track 20 on the Xenosaga THE ANIMATION Original Soundtrack. It plays in the following scenes:
 * Virgil and Shion debate the rights of Realians on the Woglinde in Episode 1.
 * Nephilim shows the party a cryptic vision of KOS-MOS and U-DO fighting in the Encephalon, and tells Shion to return to Old Miltia, in Episode 8.
 * Virgil tells Shion why he saved MOMO in Episode 9.
 * KOS-MOS proposes her plan to remove the E.S. Simeon's core in Episode 12.

A version of the track with no percussion plays when the party learns about Sakura from Jr. and the 100-series Realians aboard the Durandal in Episode 10.

The melody used at the start and throughout the piece is based on a motif from Xenosaga Main Title.