(The colored squares aren't necessary for the theme, so feel free to solve in Across Lite)
Solving Music: Hachioji P, Giga - Gimme×Gimme
Really happy that this puzzle panned out at all, to be honest. The theme felt like it wasn't going to all tie together, but I managed to find some theme entries that fit together! Even if the theme isn't lost on you, check out the solution image on this one; you'll get to see the proper formatting and everything.
That's all today; enjoy the puzzle, y'all!