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.

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