Live on stage: before the gig, during the set, when it goes wrong

What a performer needs to know about a live set on A³, as rules and checklists. Collected from the DJ reviews of the A³ documentation (2026-09-29 and 2026-10-30) and from the maintainer’s decisions. Where the rule is A³-specific, it says so; the rest holds for any booth.

The one rule behind all of them

One dropout, one crackle, one wrong jump at a gig, and the room’s trust is gone at once. Every safety rule below exists because a booth has no undo (see the booth).

When does it land? (quantised versus instant)

A performer has to know, without reading, which presses wait for the beat and which do not. On A³ Motion:

You press	It happens
Play\|Pause on a clip	on the next downbeat (the “one”)
SHIFT + Play\|Pause	now
■ (stop)	now
an action pad	now, for as long as you hold it
load a set	on the next downbeat, all four channels together
drag a blob on the sphere	now, continuously — the room hears every centimetre
record a take	the room hears what you draw while you draw it

Two consequences:

Pause lands on the downbeat (A³ decision, 2026-09-25). Stopping “at the end of the figure” felt like a dead key once figures got long (up to 16 bars); the next downbeat is what a DJ expects, SHIFT makes it immediate, and stop is the instant way out.
A drag is live. Rehearse a movement in headphones first (3d down for the room, cue on).

Before the gig

A short card, in the order a soundcheck runs:

Agree on the clock. Who is tempo master tonight? CDJs on Pro DJ Link → A³ follows the link (PIO). StemDeck only → a StemDeck deck is master, A³ Motion follows. Vinyl or a lone laptop → the beat analyser (EXT) or tap tempo (INT). The clock is not stored in sets, because every venue’s booth is wired differently: check it at soundcheck, not at the drop.
Check that the BPM shown matches the decks. A beat analyser that counts a 150 track at 75 is right for movement (a half-time grid) but disagrees with the CDJ display the DJ reads.
Room set up and saved before the doors open. Speaker calibration, front direction, levels. Saving a room setup restarts the audio with a fade — not something to do with a crowd in.
Everything visible on the desk. Decks show up on the desk’s input ring, meters move.
Recording is on, if the set is being recorded.
Developer and edit modes off. Anything that can overwrite factory content mid-set stays off.
Know what loading a set does: it stops all four movements and starts the new ones together on the next downbeat.

During the set: do not

Do not restart a deck application mid-set.
Do not save the room/engine setup mid-set (it restarts the audio).
Do not load a Motion set in the middle of a track unless the jump is the point.
Do not edit an action mid-set to suit one track. On A³ Motion an action edited on the ACTION page is changed everywhere it is used, in every set. Save a copy first.
Do not double-tap the master. A³ deliberately has no reset gesture on the master fader: it is the one gesture that would make the whole room loud at once.

Reassurances worth knowing before the gig

A restart does not move the room. If A³ Motion restarts, the sounds stay where they were; the devices come back knowing what the room is doing (Total Recall).
A³ starts silent. The outputs stay silent until every device has told the system its settings, so a reboot never blasts the room at a default level.
Delete removes the file, not the music. Whatever is loaded keeps playing; you cannot delete your way into silence.

Get me out of here (panic)

Freeze all movement now: stop all clips (on A³ Motion: Stop all, or ■ per channel).
Back to plain stereo: 3d down on a channel puts it back to plain stereo, like any mixer.
After a stop the sound stays where it stopped.

A single “all 3D off” control for the whole system does not exist yet (open as of 2026-10-30).

The hardware fader that does not move

The A³ Mixer has no motor faders. When a value changes elsewhere (on screen, in a recalled set, by the pro-DJ), the physical fader stays where it is. DJs know the answer from controllers: soft takeover / pickup — the physical control takes over when touched. Say it plainly in any interface that can move a desk value: “The physical fader doesn’t move. Touch it and it takes over from wherever it sits.” A³’s rule: a physical turn wins, and the desk shows a ring where the hardware knob stands elsewhere. For the per-stem AUX pot on the A³ Motion panel the decision went the other way: absolute, the deck wins, no pickup.

Clock: follow smoothly, never trust the source

A beat clock from outside (an analyser, a network) will report the wrong octave and the occasional stray beat. A measurement on 140 BPM music (2026-09-27) found 17 % of beats reported at the right tempo and the rest at half, and 14 % more than 20 ms off. The performer must never hear that:

treat half and double tempo as the same tempo;
need several beats (A³: 4) before accepting a real tempo change, more (16) for an octave change, and glide to it;
never jump the phase; catch up gently, and ignore a single stray beat;
if the clock goes silent, hold the last tempo rather than stopping.

One clock for the audio

Audio that travels between machines (decks on other hosts) must run on one clock. Two crystals and an adaptive resampler in between give occasional crackle, and crackle at a gig is exactly the trust loss above. A³’s rule since 2026-10-30: the Core’s audio interface is the only clock, every device follows it, no software clock, and a host whose network clock is not stable plays no deck at a gig. A multi-hour soak with zero dropouts is the release gate. (The engineering lives in a3-core.)

Troubleshooting, symptom first

Symptom	Likely cause	Do
Play blinks and never starts	no beat clock arriving	check the clock source; switch to INT and tap
The blob moves, the sound doesn’t	3d is down, or Core is not reached	raise 3d; check that meters move
Screen knob and desk fader disagree	no motor faders	touch the fader: it takes over
An action does nothing	the pad is empty	assign an action
The action sounds different from yesterday	someone edited it	restore it from the library
The desk can’t select a stem of the other deck	StemDeck’s AUTO DJ owns the stem buses while it is on (intended)	switch AUTO DJ off
Screen frozen	the application hung	restart it; the room keeps its positions