Tentacular Circus

Tentacular Circus is a song performed by Turquoise October.

Description
Tentacular Circus, like many Turquoise October songs, is an electronic song, featuring many chiptune influences, unorthodox production It appears to contain various unusual samples of vocals, whistles, bells and trumpets. It is heard in the Octo Valley missions Gusher Gauntlet, Inkrail Skyscape, Tumbling Splatforms, Pinwheel Power Plant, and can also be heard in Squid Beatz.

It makes a return in Splatoon 2, alongside Cephaloparade, and is heard in Octo Canyon missions The Octopark and The Octogalaxy. However, neither track is available in Squid Beatz 2.

Tentacular Circus (Splatoon Single Player Trailer)
Tentacular Circus was first heard in the reveal trailer for Splatoon's Hero Mode. It starts playing about 25 seconds in, cutting off Splattack!. It has an extended intro not heard anywhere else, and also has a proper ending, consisting of a modified version of the beginning.