First of all, thank you! And yes, at first I wanted the music to be a mix of both acts, but at the end I decided to only use 1 music per level. For example, Seaside Palace has Seaside Hill music, but Rail Station has Bullet Station Music. I use the music that fits the level the most.
Unless you find another suitable song for the fight versus Metal Overlord, yeah, you're kinda forced to use it. Speaking of which, pretty curious on how Boss Fights are..."What I'm Made Of" will probably be used in this mod.
Here hoping you got some skybox clouds planned for the background, because the skies do feel a little bit empty with the default background going on.