Z15f20i12e09l14d

z15f20i12e09l14d (called on the JASRAC database) is Disc 2, Track 5 on the XenobladeX Original Soundtrack. It is split into two parts: the first plays from the start until 3:04, and the second plays from then until the end.

The first part plays in the following cutscenes: A version of the first part with only vocals plays in when the party enters the Lifehold Core.
 * In when receiving the signal from the Ma-non
 * In the Affinity Mission “Manhunt” upon meeting Celica and Rock
 * In the Affinity Mission "New in New LA" when Chausson tries to convince Celica and Rock to have the latter join in fighting against the Ganglion

The second part of the track plays as the area theme in the Divine Roost of Noctilum. It is one of few area themes that takes priority over Don't worry.

Etymology
The track title can be split into 3 parts: the prefix 'z15', the digits '20120914', and the letters 'field'. The digits can be interpreted as the date 2012/09/14, or the 14th of September 2012, the date in which the track was recorded or mixed.

The track is one of several in the XenobladeX Original Soundtrack beginning with 'z' and a number (possibly followed by 'b'). The significance of this is that the composer Hiroyuki Sawano gives codenames to tracks before he properly titles them: a letter/abbreviation followed by a number, where the letter/abbreviation corresponds to the soundtrack in question. In the case of Xenoblade Chronicles X, this letter was 'z' (Xenoblade X's Japanese name, ゼノブレイドクロス, can be romanised as Zenobureido Kurosu). The number corresponds to the ordering in which tracks were composed. 'z15' is a holdover from this codename.

Therefore, 'z15f20i12e09l14d' decodes into 'The 15th track composed for Xenoblade X, a field theme, recorded/mixed on the 14th of September 2012'.