The Multiplanar City of Archtop

Archtop’s atmosphere changes how its residents hear sound.

The Third Industrial Revolution promised clean power. Its catalytic aerosols and density-modifying particles changed the atmosphere instead. High frequencies disappear above roughly 6.23 kHz. Speech sounds muffled, instruments lose their upper harmonics, and people have moved much of their music into AR.

The city treats this as a pollution problem. The Resonance Sanction Office knows that the missing frequencies are crossing into the Null Plane. Archtop's sound regulations protect a trade that its citizens have never been told about.

The atmospheric damage limits common audio equipment.

Earbuds: the same atmospheric pockets exist in the outer ear canal. Treble vanishes there too, while cheap speakers cannot reproduce enough clean bass to compensate.

Bone conduction: speech remains usable, but the cranial cavity distorts overtones. Long sessions trigger vestibular migraines. Musicians who perform for wealthy patrons rely on strong morphine-based medication to keep working.

Neural implants: a direct feed to the auditory cortex costs hundreds of millions of credits. Corporate authentication also requires access to the user's personal data and memories.

Recording and synthesis: microphones capture damaged harmonics, and atmospheric changes detune analogue oscillators. Generative systems train on recordings that are already degraded. Few people alive have heard the open-air reference those recordings were meant to preserve.

Distribution: McMillan's ministry inserts watermark tones that stop licensed devices from playing forbidden frequency profiles. Smuggling raw audio over the mesh carries the same penalty as weapons trafficking.

The setting makes censorship a material condition.

The setting makes censorship a material condition. A resident cannot speak louder or buy a better speaker. Their access to sound depends on their income, the equipment they can obtain and the risks they will take.

When adding a location, device or law, ask what it changes in the city's shared sound. Show the restriction through ordinary tasks: hearing a visitor, preparing food or making music. Let residents' workarounds explain how the city operates.

Residents adapt their daily routines to the loss of sound.

Monacon Towers has cheap AR repeaters and cracked advertising screens. “Did you pay your Silence Tithe today?” loops above corridors lined with acoustic foam. The foam bears Luther-Morrow Security's promise: “We shield you from sonic terrorism.” Residents stuff door peepholes with cotton and use AR doorbell alerts because a knock will not carry.

In the Streets and the Sinks, food stalls use vibro-pads beneath their plates to deliver taste ratings as pulses. A spatula meets the grill without a sizzle. Animated QR-code murals overlay a silently screaming mask on passers-by who scan them.

Elsewhere, mirrors return a gesture a fraction of a second late. Anti-sound frost collects on railings after bass-heavy trams pass. A bird may still sing clearly while its reflection remains motionless.

The factions compete to control access to sound.

Regent Dorian McMillan governs from the Cathedral of Silence. He believes an unregulated concert could awaken the Fathom-Lord and exchange Archtop with its Null reflection. The Resonance Sanction Office enforces the Decibel Tithe, while some of its researchers question the original catastrophe models. Luther-Morrow Security supplies the enforcement: acoustic infrastructure and infrasonic crowd-control weapons.

Neon-Dream Mire sells sensory trips and harvests customers' overtones. It trades those frequencies to the Polyphonic Depth for predictions. The Tonewood Guild hides instruments in cedar-oil bunkers beneath bathhouses. Netdiggers steal Chorus Keys from closed RSO laboratories to open brief tunnels into the Null Plane.

The Refrain Breakers bring together performers and instrument makers who want shared sound back. Frequency Forward pursues a Silence Bomb that could seal the breaches, with a citywide coma among the predicted costs. The Polyphonic Depth cult plans the Grand Detuning, a concert using the city's ducts and tunnels as a single tuning fork.

The rising tithe puts more of the city’s sound at risk.

The RSO demands just over two gigajoules of upper harmonics each day. The tithe rises quarterly, and surveys show the frequency threshold falling by about seventy hertz a year. Ordinary speech may eventually cross it.

Researchers are testing whether an anti-phase anthem could collapse the Resonance Lattices. A failed attempt might widen the breaches. For the cosmology, entity hierarchy and competing plans, read The Null Plane.