Inside the Deepsea Metro Subway Car

Inside the Deepsea Metro Subway Car is a song played in Splatoon 2's Octo Expansion in the Deepsea Metro train.

Description
Inside the Deepsea Metro Subway Car is an ambient electronic track. Variations of the track are played whilst in the Deepsea Metro train. It consists of a repeating kick and snare loop, as well as a synthesizer bass. Soon after, an ascending synth melody is heard and repeats throughout the rest of the track. Some synth chords are played and are repeated at the same interval multiple times. When the synthesizer chords first start playing, the main opening melody to the Calamari Inkantation plays very faintly on a xylophone-sounding instrument. This melody repeats a few more times in the loop. Further on, some unknown, presumably Inkling, noises are heard. After these stop, another strange sound is played, sounding like a conductor talking through a train microphone. After this, the track loops. The song changes and develops depending on how many Thangs have been unlocked. The final version is heard in the Deepsea Metro Subway Car, when in the Deepsea Metro after collecting all four Thangs. After a new variation is unlocked, the previous variations cannot be heard when in the car.

Inside the Deepsea Metro Subway Car (No Thangs)
The first variation is much more stripped back. It has weaker sounding kick drums, lacks the synthesizer and Calamari Inkantation interpolation, and only one chord is played throughout at the same rhythm each time. It is heard in the Subway car before collecting the first thang.

Inside the Deepsea Metro Subway Car (1 Thang)
The second variation includes the first variation, but with a heavier sounding kick drum. It is heard in the Subway car after collecting the first thang, but before the second thang.

Inside the Deepsea Metro Subway Car (2 Thangs)
The third variation includes the second variation, but the synthesizer chords play at the very start of the loop, and now plays multiple different chords instead of one throughout the whole piece. The chords also now play at a different rhythm and with different intervals between them. It is heard in the Subway car after collecting the second thang, but before the third thang.

Inside the Deepsea Metro Subway Car (3 Thangs)
The fourth variation includes the third variation, but the Calamari Inkantaion interpolation is added. Compared to the final version, it lacks the heavy sounding snare and kick loop which repeats throughout the whole song. It is heard in the Subway car after collecting the third thang, but before the fourth (and the final) thang.

Inside the Deepsea Metro Subway Car (Octotune)
In Octotune, a medley of all the versions is included instead. The No Thangs version plays until roughly around 0:57, which than it switches to the 1 Thang version. At around 1:45, it switches to the 2 Thangs version, and it switches again at around 2:33 to the 3 Thangs version. From roughly 3:20, it than switches to the final version, which plays for the remainder of the track until it fades out.

Trivia

 * According to a Famitsu interview, Sound Director Minegishi comments that use of the Calamari Inkantation can be constructed as Agent 8's auditory hallucination, an inner melody of their mind that intensifies as more of their memory returns.