This project has the theme from the octo expansion trailer, cut so you don't have to. Meaning: The music has three parts: A beginning, a main part, and an ending. In a project, we only need the first part to play once, then to play the main part over and over, and the ending is mostly useless. So I split the parts for others to use.
I got the music from SANSXXTORIAL (see below) who got it (perhaps indirectly) from the trailer made by Nintendo. Hype stuff.
