WHAT did I just watch?
Jokes aside, the discussed Category-5 or Mastermind Tsi-Hu could issue its commands through a music-like noise that could maybe only be perceived by researched specialized equipment tuned to a certain frequency. And through analysis and breakthroughs from the research department, Reapers or more likely, some field support units, deployable, defendable mobile sensors could eventually be able to produce sounds that could temporarily disrupt the communication of the Tsi-Hu, disorienting them.
As for underground bands...Borderlands 3 featured some barely known bands that had some great soundtracks. And good way to promote such less known but promising bands is to feature them in such ambitious projects. Or for another example, the band
Poets of the Fall, using the name Old Gods of Asgard in the Alan Wake games, created songs just for the game itself and for a related title CONTROL, which also featured one of the real band's best songs. Such collaborations would go a long way of not only mutual promotion, but enriching the game-world, again, to make it more real.