The hum was maddening.
It wasn't loud enough to burst eardrums, but it was deep enough to rattle teeth. VVVVVVVVVVVV.
Inside the BK Building, the trainees were curled up on the floor of the practice room, hands over their ears. Some were vomiting from the vertigo induced by the low frequency.
"It's 18 Hertz," Eden analyzed, standing by the window. The blinding white light from Zenith Tower washed over his metal frame. "The 'Ghost Frequency.' It causes anxiety, paranoia, and hallucinations in biological brains."
"Can you filter it?" Yoo-jin shouted over the vibration.
"I can cancel it for myself," Eden tapped his head. "But not for the building. The sound waves are penetrating the brick."
"We can't work like this!" David Kim paced, clutching a bottle of aspirin. "We can't record vocals if the mic picks up a constant earthquake!"
"That's the point," Yoo-jin walked to the massive concert speakers they had dragged up to the roof. "Mason wants us to fold. He wants the trainees to run back across the street begging for silence."
Yoo-jin looked at the massive black wall of Zenith Tower. He could see the spotlights mounted on the balconies, glaring like the eyes of a monster.
"Connect the rig," Yoo-jin ordered.
"Yoo-jin," Sae-ri shouted, shielding her eyes from the glare. "You can't out-shout a skyscraper! They have industrial amps. We have tour gear."
"We're not shouting," Yoo-jin plugged a laptop into the mixing board.
He opened a waveform editor. He recorded five seconds of the hum.
VVVVVV.
On the screen, it was a flat, ugly sine wave.
"It's a G-sharp," Yoo-jin noted. "Tuned specifically to be dissonant."
He started typing. He added a beat. He added a synth layer.
"If you can't stop the noise," Yoo-jin grinned, the blue light of the laptop reflecting in his eyes. "Make it the bass line."
The next morning, Teheran-ro was gridlocked.
Office workers on their way to Zenith Tower stopped on the sidewalk. They looked up, confused.
The nauseating hum was gone. Or rather, it had changed.
Boom. Boom-clap. Boom.
A massive, heavy beat was shaking the street. It was synced perfectly with the vibrating hum coming from Zenith Tower.
The hum wasn't a weapon anymore. It was the intro to a track.
On the roof of the BK Building, Min-ji stood on the edge, holding a megaphone.
"Good morning, Gangnam!" she screamed.
Behind her, the massive speakers blasted Yoo-jin's remix. He had taken Mason's psychological warfare and turned it into a heavy industrial hip-hop beat.
The trainees weren't curled up on the floor anymore. They were on the roof, dancing.
Dong-soo, the boy with the torn pants, was leading them. He moved with the jerky, aggressive energy of the beat. It wasn't clean choreography. It was a street battle.
"What is that?" A Zenith employee on the street stared up. "Is that... music?"
"It sounds like a club," another muttered, tapping his foot unconsciously.
Inside the Chairman's Office on the top floor of Zenith Tower, Mason Gold stood by the window. He looked down at the red brick building pulsing with sound.
"He sampled my attack," Mason whispered, crushing his coffee cup. "He turned my siege into a rhythm section."
"Shall we increase the frequency?" Director Park asked, her avatar flickering on the screen.
"No," Mason turned away. "If we change it, he'll just remix it. He's monetizing the conflict."
Mason looked at the crowd gathering on the street below. People were filming the rooftop party with their phones.
#StarforceRoofParty was already trending.
"Fine," Mason sat down. "If he wants a war of decibels, let's give him a competitor."
He pressed a button on his desk.
"Deploy 'The Sirens'."
The party on the BK roof stopped abruptly at noon.
Not because the music stopped, but because three massive holographic projectors ignited on the side of Zenith Tower.
Three figures appeared, fifty stories tall. They were beautiful, glowing women with wings made of fiber-optic cables.
[New Debut Group: THE SIRENS]
[Zenith Entertainment]
They opened their mouths.
It wasn't a song. It was a weaponized vocal harmony. A sound so pure and high-pitched it shattered the windows of a nearby coffee shop.
AAAAAHHHHHHH.
The sound cut through Yoo-jin's remix like a laser. The trainees on the roof clamped their hands over their ears, screaming.
"Feedback loop!" David yelled, diving for the mixing board. "They're overloading our amps!"
POP.
Smoke poured from Yoo-jin's speakers. The music died.
The Sirens continued to sing. It was opera, but distorted. It sounded like angels screaming.
"They blew the speakers!" Min-ji kicked the smoking amp. "That's cheating!"
"It's a vocal attack," Sol listened intently, wincing. "They're hitting a C6 note. It's impossible for a human. Those are AIs."
Yoo-jin looked at the giant holograms looming over them.
"He's escalating," Yoo-jin wiped soot from his face. "He's not just making noise. He's debuting his new weapon right in our faces."
The Sirens weren't just loud. They were hypnotic.
Down on the street, the crowd stopped filming. They stared up at the holograms, entranced. Their expressions went slack.
"They're mesmerizing the public," Sae-ri realized. "It's the Violet Signal again, hidden in the music."
"We need to cut the feed," Kai said. "Shoot the projectors?"
"They're behind bulletproof glass on the 40th floor," Yoo-jin shook his head. "We can't shoot them."
He looked at his fried speakers. He looked at the entranced crowd.
"We can't out-sing them," Yoo-jin admitted. "Not with volume."
He turned to the trainees huddled against the wall.
"Dong-soo. Ha-eun. Everyone."
They looked up, terrified.
"Do you know why opera singers can shatter glass?" Yoo-jin asked.
"Resonance?" Dong-soo guessed.
"Exactly," Yoo-jin pointed at the Zenith Tower. "That building is covered in glass. Thousands of panes of tempered glass."
He pulled out his phone. He opened the frequency analyzer app.
"Those holograms are hitting a specific pitch to hurt us. But every pitch has a counter-pitch."
He looked at Sol and Luna.
"Can you hit a low F?"
"Low F?" Luna blinked. "That's barely audible. It's a rumble."
"I don't need people to hear it," Yoo-jin said. "I need the building to feel it."
He turned to the massive water tank on the roof of their building—the "bad plumbing" Mr. Choi had warned about.
"Eden. Min-ji. Drain the tank."
"What?"
"Empty it," Yoo-jin commanded. "It's a giant metal drum. If Sol and Luna sing into it at the right frequency, we can turn this whole building into a subwoofer."
Ten minutes later.
The Sirens were still screaming their high note. The crowd on the street was zombie-like.
On the BK roof, Sol and Luna stood with their heads inside the empty, rusted water tank.
"It smells like rust," Luna complained.
"Focus," Yoo-jin stood by the metal tank, his hand on the surface. "Match the vibration. Feel the Sirens' note... and go under it."
"Now!"
Sol and Luna began to hum. Low. Deep. A vibration that started in their chests and echoed in the hollow metal tank.
Hmmmmmmmmmm.
The tank began to vibrate. The rust flaked off.
The vibration traveled down the pipes of the BK building. Into the ground. Under the street.
And up the foundation of Zenith Tower.
Inside the glass tower, employees felt it first. Coffee cups rippled on desks. Computer monitors shook.
Rattle. Rattle. Rattle.
The Sirens' high note was clashing with the low rumble from across the street.
"Resonance interference!" Director Park shouted in the Chairman's office. "Structural integrity at 98%... 95%..."
The massive glass windows of the Zenith lobby began to wobble. They were vibrating in time with Sol and Luna's hum.
"Push it!" Yoo-jin shouted, feeling the tank shaking violently.
Sol and Luna closed their eyes. They dropped their pitch one octave lower.
CRACK.
It started with one window on the 10th floor. A spiderweb fracture appeared.
Then the 11th. Then the 20th.
The Sirens' hologram flickered. The projectors were shaking out of alignment.
SCREEE-BLIP.
The angelic singing distorted into a glitchy mess.
The crowd on the street woke up. They looked around, confused.
Then, the glass rain began.
SMASH.
A pane of glass from the 5th floor shattered, raining shards onto the Zenith plaza.
"Evacuate the lobby!" Security guards screamed, running for cover.
"Stop!" Mason roared in his office, holding onto his desk as the floor shook. "Turn off the Sirens! They're shaking the building apart!"
The holograms vanished. The screaming stopped.
Silence returned to Teheran-ro.
Except for the low, triumphant hum coming from the rusted water tank on the red brick building.
Hmmmmmm.
Yoo-jin patted the tank.
"Good job," he told the twins.
He walked to the edge of the roof. He looked at the Zenith Tower. It was still standing, but dozens of windows were cracked or broken. It looked scarred.
The "perfect" tower was flawed.
He picked up the megaphone.
"Hey, Mason!" Yoo-jin shouted. His voice echoed off the glass facade.
"You owe me for a new speaker system!"
Down on the street, the crowd started cheering. They didn't know the physics. They just knew the underdogs had won the noise war.
A young girl in the crowd held up her phone. She was streaming.
"Did you see that?" she yelled into the camera. "Starforce just cracked the tower!"
Yoo-jin lowered the megaphone. He turned to the trainees.
They were staring at him with awe. The fear was gone.
"Lesson one," Yoo-jin said, dusting off his suit. "If the stage is too loud... break the venue."
He checked his watch.
"Lunch break. Then we record."