I like the idea of both the game influencing the music and the music influencing the game.
Like, you have a directed graph of music, with audio on the edges, and the current game state determining which edge one takes out of a node. The game influences the music there.
But then you also have an "event track" on the edges that can be used to do cosmetic things like flash lights in the game or whatnot in time with the music, or, as with rhythm games, require the player to do things in time with the music. There, the music influences the game.
Or one step further, let the music slightly alter the timing of non-cosmetic events. E.g. player throws grenade, game sends approximate explosion time to the music player, which transitions to an appropriate build up and sends the exact explosion time back to the game. Explosion visuals, SFX and music all line up perfectly.
Yeah the newer music-based games are pretty cool. Maybe as stuff like OpenRGB becomes more standard we could also see that tied into game/music events more as well