Well, considering I was part of a "tactical sound unit" back home, a few things. [Mikumo's tone is lightly amused, though she can't say it's entirely a common application to use it in combat in her world, either.] There's something of a tendency in the universe I come from for unexpected things to respond to music, so while it's not used as a weapon, per se, it's been used in combat a number of times. [Technically, it has been used as a weapon on occasion, but broaching that topic opens her up to questions she'd rather not answer.] Certain threats respond to it - even non-sentient ones. My unit responded to outbreaks of Var Syndrome, a condition caused by a certain type of alien bacteria acting up in its hosts that drives people into mindless violence. Our singing voices essentially nullified the effects of the bacteria.

[Fold waves and fold receptors are a bit of a weird topic to get into, since fold technology is used for a number of things in her world and not all of them make a whole lot of sense to...most people, really, so she's keeping the explanation relatively simple.]