Harmony Kendall had, like, the biggest family secret ever.
Though, what she really resented over the years about that exact skeleton in the closet, was how it'd made all her friends since kindergarten up to Sunnydale High think Harmony was the dumbest girl in class. That was just totally unfair!
If she'd only had the chance to stop concentrating every single waking moment to keep from spilling the beans and be able to relax once in a while, Harmony was sure people would actually think she might be smart.
But, nope, it was Great-Granny Elel's fault, passing that horrible surprise onto the next female generation, followed by the next after that, and so on, who had to deal with it the best they could at the time. Unfortunately, it seemed to getting much worse at every occurrence for this progression of Kendall daughters, finishing off with Harmony herself.
The last remaining penny in the trust fund discreetly set up decades ago by Great-Granny Elel's deaf husband when his spouse refused to believe there was any kind of problem had finally been used up in hiring numerous expensive therapists and tutors for Harmony before she'd entered preschool.
Still, they'd stoically accomplished their difficult task of teaching the little blonde girl to never reveal to anyone what she could do, no matter what. It'd been a long, hard battle, but Harmony Kendall eventually learned to talk just like any other child rather than someone standing at the center of Times Square who could shatter every skyscraper window in Manhattan with the shrillest voice in the entire world.
Of course, when that vampire at the latest SHS graduating ceremony targeted Harmony in the middle of the fight between the Scoobies, the other students, Mayor Wilkins, and the rest of the attacking demons, a terrified young woman forgot all her strict long-ago lessons and screeched at the top of her lungs towards that advancing monster, "LEAVE ME ALONE, YOU JERK!"
Struck head-on by an amplified bellow resembling gargantuan fingernails scraping across a mile-wide blackboard, the vampire dropped in his tracks, uncontrollably convulsing on the schoolyard grass. He wasn't alone. A good many nearby demons with equally sensitive hearing also suffered various fatal injuries, including a certain spiky-haired Billy Idol lookalike, whose brains basically poured out of his ears before this blood-drinker limply fell flat on his face.
Even the enormous serpent chasing that nuisance of a Slayer forgot about this escaping prey when vibrating agony racked his entire reptile body from an unexpected hideous racket from behind. Wanting only to get as far away as possible from that ghastly auditory assault, a fleeing Mayor Wilkins hastily overtook Buffy Summer diving out of the way to the side, and plunged directly into the high school building in the hopes of finding a safe hiding place there.
Which then promptly exploded.
Getting up to her feet with ringing ears several moments afterwards, Harmony ignored the awed looks being sent her way by every human survivor. Instead, she grumbled to herself, "Oh, thanks so much, granny! Looks like just in your silent movies, Lina Lamont saved the day again! Except that I don't get the handsome guy, either, same as when you got caught by Don and Kathy and had to retire from show biz in total humiliation!"
Disclaimer: I own nothing. All Buffy the Vampire Slayer characters and Singin' in the Rain characters are the property of their rightful owners.