The obsidian staircase connecting the ash-trenches to the Seventh Ridge bit into the soles of Thura’s calloused feet, slick with condensed sulfur grease. Higher up, the heat lost its greasy, sulfurous thickness, replaced by the crisp, mineral bite of mountain draft. Here, where the overseers lived in hollowed stone villas, the ground did not simply shake; it hummed with an uneven, discordant oscillation that made Thura's molar crowns throb behind her closed lips. Beside her, Jorik stumbled, his fingers digging into his scalp until red rivulets tracked through his greasy black hair. His mouth was stretched open in a soundless mimicry of terror, his throat working violently. He was drowning in the sound Thura could only register as mechanical dissonance. She caught his shoulder, fingers sinking into the thin hollow above his collarbone, and dragged him behind a decorative parapet of black volcanic glass. Down the flagstone alleyway, someone was ruining the earth. It was not a scream of agony, though pain clearly fueled it. It was an involuntary flute-note, warped and piercing, that shuddered through the dark pavers beneath Thura’s toes. The rhythm was erratic—three fast, sputtering trills followed by a long, ragged whistle that set the dust skittering in frantic rings. Deep below, thirty leagues down in the magma gutters, the tectonic maw responded. Thura felt the subterranean reply: a dull, rhythmic grinding of thousand-toothed rings chewing through mantle rock, rising closer to the crust. Thura crept forward, leaving Jorik curled into a fetal knot against the wall. In the shadow of an ash-stained archway lay Overseer Drelka. The woman who had thrice broken Thura’s ribs with an iron measuring rod was on her knees, clawing at her own throat. Drelka’s thick neck had split down the thyroid cartilage. Jutting through the torn muscle were translucent, smoky-gray needles of volcanic silica, fused into her larynx like the pipes of a miniature water-organ. Each time her chest convulsed, air forced through the crystalline perforations produced a shrill, fluttering harmonic that cracked the slate roof-tiles overhead. Drelka looked up, her bloodshot eyes bulging with terror as she recognized the trench-sweeper. Her thick fingers, scarred from years of brandishing the lash, reached outward in a plea for aid. Her lips formed jagged shapes: *Help. Pluck them. Cut them out.* Thura felt neither pity nor vengeance. Looking at Drelka was no different than inspecting a cracked sluice gate or a rusted steam-piston. The woman was venting air inefficiently. The leak was creating parasitic turbulence, agitating the blind leviathans beneath the floorboards instead of soothing them. Thura crouched beside the writhing taskmaster. Drelka gasped, reaching for Thura’s wrist, but Thura knocked the heavy hand aside with the edge of her wooden ash-shovel. Carefully, Thura placed her bare heel squarely over Drelka’s sternum. Drelka stared up in stark panic, veins bulging across her temples like blue cords. She tried to roll, to throw the deaf girl off, but Thura shifted sixty kilos of lean, trench-hardened mass directly onto the woman’s rib cage, pinning her flat against the cold pavers. Thura leaned down, pressing her palm against the stone inches from Drelka’s neck to read the tremors. *Too shrill. The bore is too wide; the air escapes in chaotic bursts.* Thura pressed down harder with her foot. Her heel sank into the soft muscle between Drelka’s ribs, compressing the thoracic cavity like an artisan depressing a leather forge bellows. Drelka choked. Her face darkened to a mottled plum hue, but the forced contraction pushed a single, pressurized blast of air through the glass-coated throat. The pitch changed instantly. It climbed two octaves, flattening from an erratic shriek into a sustained, razor-sharp whistle. Through her palm on the flagstone, Thura monitored the result. The localized tremor that had been rattling the alley’s foundation slackened. The crawling, grinding sensation fifty yards below smoothed out, the tectonic worm retreating a fraction of an inch into its subterranean tunnel, lulled by the momentary purity of the high-register note. *A bellows,* Thura realized. *The lungs are simply the bellows. The glass needles are the reeds. But the chamber is untuned.* When Thura relaxed the pressure on Drelka’s chest, the woman dragged in an uncontrolled, ragged breath. The glass vocal cords rattled against each other with a sickening clatter, and the pitch immediately collapsed back into a discordant squawk. Beneath their feet, the stone jarred violently, a crack snapping open between two paving stones and releasing a puff of sulfurous white smoke. Drelka was sobbing now, thick, viscous saliva foaming at the corners of her mouth, mixed with specks of vitreous ash. Her hands gripped Thura’s ankle, trying to pry the trench-sweeper’s foot loose, but her strength was fading from oxygen starvation. "Keep your wind steady," Thura said. Her own voice sounded hollow in her skull, a flat vibration of vocal cords she had not used in months. She didn't care if Drelka could parse the words; the instruction was mechanical. Thura reached into her tool belt and pulled out a pair of heavy iron shears, typically used to snip through wire mesh in the slag sifters. She gripped Drelka’s chin, forcing the overseer’s head backward until the woman’s neck was taut against the curb. The cluster of crystal spines protruded like an irregular comb, glistening with blood and lymphatic fluid. Three of the needles on the left flank were longer than the rest, vibrating at a frequency that clashed with the central whistle. They produced an ugly undertone, the very beat-frequency that was agitating the worms. Thura set the iron jaws of the shear against the longest needle. Drelka thrashed, her boots hammering the stone, hands clawing at Thura’s thighs. Thura ignored the nails tearing through her canvas trousers. She squeezed the handles with the callous-hardened grip of a digger who spent twelve hours a day levering basalt boulders. *Snap.* The glass shard sheared clean. Drelka let out a strangled, bubbling shriek that hit a pure, bell-like clarity. Thura clipped the second needle by half its length, shortening the bore. Then the third, notching it with the shear’s serrated edge to alter its airflow. With every modification, Thura kept her left palm planted firmly against the pavement, feeling the earth’s response. It was precise work. A millimeter too short, and the pitch would skip an octave, potentially angering the subterranean horrors into an immediate breach. A fraction too long, and the mud-thick undertones would shake the Seventh Ridge loose from the crater wall. She leaned her full weight onto Drelka’s chest again, regulating the woman's exhalation into a rhythmic, measured cadence: three seconds of compression, two seconds of intake. The resulting sound did not register to Thura’s ears, but she felt its perfection through her bones. It was a cold, pure note, like grease applied to a screeching iron axle. Ten leagues down, the chittering vibration of Maw-Worm mandibles ceased entirely, soothed into a temporary torpor by the harmonic ring. Yet, this was only a single pipe. A solo treble note could quiet a juvenile worm near the crust, but the grand leviathans sleeping in the deep rift magma required a full, polyphonic counterpoint. A bass foundation. A midrange drone. Thura looked up the terraced slope toward the summit. Perched atop the caldera’s highest precipice sat the grand obsidian keep of Baron Morvath. Even from here, she could see a faint, crystalline shimmer rising like heat-haze above the estate’s chimneys. A deep, heavy rumble—a discordant, booming bass note—throbbed through the bedrock from that direction, strong enough to shake loose dust from the alley walls. Morvath was mutating, too. But his voice was too vast, too monstrously loud, drowning out the fragile balance she had just carved into Drelka’s neck. Thura looked back down at the weeping overseer. Drelka lay limp, chest heaving under Thura's heel, her breath escaping through the trimmed glass pipes in a continuous, forced chime. Blood seeped into the collar of her fine tunic, but she was alive. She was functional. "Get up," Thura muttered, though she did not ease the weight on the woman's ribs. She uncoiled a length of heat-treated chain from her hip. She would need to haul Drelka down to the Caldera Vents, where the natural geothermal drafts could keep those glass lungs pumping without Thura having to stand on her all day. But first, she needed the rest of the choir. She needed the centerpiece. A violent jolt rattled the alley, knocking Jorik flat against the pavers. From the high terrace above, Baron Morvath’s estate gave off a resonant, glass-shattering groan that made the city’s foundations tilt three degrees toward the lava sea.

The Acoustic Engineer