X-BT4

X-BT4 is Disc 4, Track 7 on the XenobladeX Original Soundtrack. It is a version of no4=D91M with no percussion (most noticeable at 2:07 in the track).

It plays in the following cutscenes:
 * Elma and Lin explain the idea behind mimeosomes to Cross.
 * Lao agrees to give back the data terminal in.
 * Adolphus opens the safe at the end of Gold Rush.
 * Loda Gorida speaks with the party after they fight Leroy's Ire during Forbidden Love (if the player doubted that Leroy could take care of Lavina Couba).

Etymology
The track's title is most likely an acronym for '(Xenoblade Chronicles) X - Bonus Track 4'.