air: 20 HP, an effect you play by breathing, by daylight noise

Under the water

The sound at IN goes under the water, and the column of lit bubbles up the middle is the air you have left. It falls for as long as you don't surface, and as it falls the sound sinks: it goes darker, sags in pitch and drags like tired tape, gathers rising bubbles and drowns in a growing murk. The sag keeps time: however long it sinks, it never falls behind. The window at the top dims from daylight to a deep blue.

IN L and IN R: the sound, in stereo. IN R takes IN L when nothing's in it.

DEPTH: how far it can sink. Down, a damp pool: even out of air it only goes a little dull and wet. Up, the abyss: out of air, a muffled thud an octave down, almost all murk.

DEPTH CV: ±5 V adds or takes away half the knob.

LUNGS: how long the air lasts, from two seconds to four minutes.

Breathing

Press SURFACE, or send its jack a gate, and it gasps: the air comes back and the sound breaks the surface. Hold it, or hold the gate high, and it stays up there; let go and it sinks again. With LUNGS short, a clock into SURFACE pumps it: plunge and gasp on every beat.

SURFACE: the button, and a gate in under it. The window flashes white at each gasp.

GASP: how hard it breaks the surface. Down, a slow swell up out of the murk over two seconds. Up, a violent burst: bright, dry and loud for a moment in a roar of air, the column full at once.

Drowning

Let the air run out and it drowns: the sound sinks into the murk and fades to nothing over a few seconds, longer the deeper it goes. It stays silent until the next SURFACE brings it back.

With PANIC up it fights. From half empty a heartbeat comes up, from 60 to 150 beats a minute as the air goes, and the sound flutters and stutters as bubbles burst out of it. What's left of the column and the rings round DEPTH beat red with the heart.

PANIC: down, it sinks quietly, at peace; up, panic sets in from half empty.

DROWN: a trigger the moment the air runs out.

AIR: the air left as a voltage, 8 V full to 0 V empty.

OUT L and OUT R: the sound, in stereo.

Sonar

Press SONAR, or trigger its jack, and a ping goes into the water: a short rising chirp. Its echoes come back off a cave you can't see, each fainter and darker than the last. The rings round DEPTH light outward with the ping and back inward with each echo.

SONAR: the button, and a trigger in under it.

CAVE: the space down there, for the echoes and the murk both. Down, a tight cave: echoes in tens of milliseconds, a ringing comb, the murk a short metallic flutter. Up, the open abyss: echoes seconds later, scattered, and a vast dark murk.

The panel

Twenty HP, every part on the line's staggered grid and mirrored about the middle: the left side breathes, the right side is the deep. Under the name is the surface window, a round of circuit board lit from behind, like Snell's window, the circle of sky you see from under water. The air column rises up the middle to it, and three rings round DEPTH light for the sonar. The art is hands reaching up for the light.

IN L, GASP, LUNGS and OUT L down the left; IN R, CAVE, PANIC and OUT R down the right.

SURFACE and SONAR either side of the window, each with its jack under it, marked with a pulse.

DEPTH in its rings, AIR and DROWN beside it, DEPTH CV at the foot.