Z39b20co13mi01cal09

z39b20co13mi01cal09 (called on the JASRAC database) is Disc 2, Track 6 on the XenobladeX Original Soundtrack. It is split into two parts: the first plays from the start until 1:36, and the second plays from then until the end.

The first part of the track plays in the following cutscenes:

Main story

 * The party discovers and frees Tatsu from a storage container in.
 * Tatsu is introduced to in Chapter 3.
 * Lin suggests Tatsu make the refrigerator his room in.
 * At the starts of Chapters 4 through 12, when Lin is cooking and uses Tatsu to make food jokes.
 * L approaches the party in.
 * The party first meets the Ma-non in.
 * Tatsu sympathises with Lao's team members in the Affinity Mission "A Friend In Need".
 * The party learns Shingo has a crush on someone in the Affinity Mission "The Matchmaker".
 * The party negotiates with the Ma-non craftsman in the same mission.

Sidequests

 * Alexa asks Cross to help her with testing a Skell's weaponry at the start of Weaponized.
 * The party asks Mujiji if he can sell them aerozium during Fitting In.
 * Lin notices that Doug has walked off without paying for his coffee at the end of Soldier of the Harriers.
 * Frye introduces himself to the party by offering to buy them drinks at the start of Bottoms Up.
 * Frye offers to work with the party again at the end of the same mission.
 * The party first meets Phog at the start of Foggy Dilemma.
 * Phog realises that he accidentally investigated a place twice in the same mission.
 * Phog briefs the party on the mission to investigate odd things out in Oblivia at the start of A Great Divide.
 * Frye and Phog reminisce on old times after the unsuccessful and successful attempts at obtaining the Phogrium during Brotherly Love.
 * Pulala introduces herself to H.B. during The King of Fear.
 * Lularita greets Hope during A Present for Hope.
 * L requests that the party gather materials to expand his business during L's Conundrum.
 * L sells his new wares to NLA citizens during the same mission.
 * requests that L and the party help him obtain the ancient Nopon remedy during The Nopon Heir.
 * Tora claims that the Nopon remedy requires a Guardian Etherscale during the same mission.
 * Tora consumes the ancient Nopon remedy at the end of the same mission.
 * Tora meets up with Mia at the start of Mia Grows Up.
 * Nan tells the party how Tora must acquire a coin for the Nopon Commerce Guild in the same mission.
 * Nan explains the procedure for forging the Nopon Commerce Guild coin after the materials are acquired in the same mission.
 * Tora's mamapon tells Tora about the bird that took his dadapon in the same mission.
 * The party finds Dadato in the same quest.
 * Tora tells Tatsu he knows the whereabouts of Dodonga Caravan at the start of.
 * Tatsu arrives at Dodonga Caravan for the first time in the same mission.
 * The party decides to search for Tatsu's dadapon's glasses in the same mission.
 * Tatsu puts on his dadapon's glasses in the same mission.
 * Tatsu proposes that the Dorian Caravan form an allegiance with NLA during BFFs.
 * The Nopon of the Dorian Caravan rejoice after the party pays them handsomely for their allegiance in the same mission.
 * Tatsu enjoys his birthday feast at the end of To Serve Nopon.
 * The party suggests that has been slacking off at the start of A Day in the Life.
 * The party observes Vandham relaying orders over breakfast in the same mission.
 * Vandham advises Skell mechanics later on in the same mission.
 * The party learns that Vandham has rushed off since they gathered required materials in the same mission.
 * Yelv announces that the party are now his partners during Meeting Yelv.
 * Yelv searches Mission Control for a task befitting a Reclaimer in the same mission.

The second part plays in the following cutscenes:

Main story

 * Lin brings Cross on a tour throughout New Los Angeles in.
 * The opening cutscene of the Affinity Mission "Renewed Will".
 * Meeting up with Lao in the Affinity Mission "Close Comrades".
 * Lin and Vandham introduce the Skell with the Flight Module to Cross in the Affinity Mission "A Girl's Wings".

Sidequests

 * Tika debriefs Alexa and the party on their test of Tika's Skell during Weaponized.
 * Alexa excitedly rambles about weaponry testing after trying out the Ramjet Rifle in Sylvalum in the same mission.
 * Tika briefs Alexa on testing out the Sparkjet Rifle during What the Skell?!.
 * Elma tells her team to escort her to a certain place in Primordia at sunset at the start of Then and Now.
 * Hope rejoins with Ornella at the end of Hope Springs Eternal.
 * Cross updates Ada on their findings regarding Hope's father's journal's whereabouts during A Present for Hope.

A very small portion of the second part (1:59 to 2:07 in the track) with no accompaniment plays on the results screen for Squad Missions, Time Attack Missions and Support Missions.

Etymology
The track title can be split into 3 parts: the prefix 'z39b', the digits '20130109', and the letters 'comical'. The digits can be interpreted as the date 2013/01/09, or the 9th of January 2013, 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. 'z39b' is a holdover from this codename.

Therefore, 'z39b20co13mi01cal09' decodes into 'The 39th track composed for Xenoblade X, comical theme, recorded/mixed on the 9th of January 2013'.