@Garison DeCrick I've occasionally reflected on a similar concept with dubstep-visualizers, as in the way the bars at the bottom of the screen or around the centerpiece jump out in wave formations in time to the music. A game could probably be themed around incorporating music visualizers into the danmaku, possibly with a different style for each boss and having that boss's theme tailored to the attack style.
I haven't yet looked into Barrage Musical ~ A Fantasy of Tempest, but I've heard it's danmaku is designed to be in time to the music; possibly this is a concept that could be adapted into the visualizer idea? I'd assume this requires a rework of the way battles progress; as it is now, everything would have to be timed attacks to prevent the music from falling behind.
Also the way the MIDI bars are glowing in this video made me think of this.