Interactive installations fail in boring ways. The video starts before the lights. The sound doesn’t loop cleanly. Something needs restarting and the only person who knows the order is you, and you’re not there.
QLab is the answer theatre worked out decades ago and most of the art world still hasn’t adopted. It’s a macOS application from Figure 53 that runs a numbered list of cues — audio, video, lighting, MIDI, OSC, scripts — in a defined order, triggered by a keypress or a clock or another cue. The basic tier is free and genuinely sufficient for small work.
If your piece has more than one thing that must happen in sequence, this is the tool.
The mental model
Everything is a cue in a cue list. You select a cue and press GO (the space bar). That’s it.
The power is in what a cue can be and how cues chain. Cue types you’ll actually use:
- Audio — playback with levels, fades, looping, device routing
- Video / Camera — playback and live input, with geometry and opacity
- Fade — change the parameters of a running cue over time
- Wait — do nothing for n seconds
- Start / Stop / Pause — control another cue
- Group — contain other cues
- MIDI / OSC / Network — send messages to other hardware and software
- Script — run AppleScript for anything else
Your first cue list
- Drag an audio file into the workspace. You get an Audio cue.
- Select it, press GO. It plays. That’s the whole loop.
- In the inspector, set Infinite Loop for ambient sound.
- Add a Fade cue targeting it, set the target level to −∞ dB over 5 seconds. Now you can fade it out on a cue rather than yanking it.
The important habit starts here: number your cues deliberately (10, 20, 30 rather than 1, 2, 3), so you can insert 15 later without renumbering everything.
Auto-continue vs auto-follow — learn this early
Two settings on each cue that determine whether GO is needed. Confusing them is the most common beginner problem.
- Auto-continue — fire the next cue immediately when this one starts. Use it for things that must happen together: lights and sound on one GO.
- Auto-follow — fire the next cue when this one finishes. Use it for sequences: video plays, then the next thing happens.
Chain these and a single GO can run an entire timed sequence. That’s how you build an installation that runs itself: one cue to start, everything after it on auto-follow and waits.
Groups, and the four modes
A Group cue contains other cues, and its mode decides what happens on GO:
- Start all children simultaneously — the default; everything at once
- Start first child and continue — the group behaves like a cue list you step through
- Timeline — children start at specified offsets, like a mini sequencer
- Playlist — children play one after another, as a queue
Timeline mode is the one that makes complex moments manageable: one cue containing a whole synchronised event with offsets, instead of a fragile chain of waits.
Talking to the rest of the rig
This is where QLab stops being a media player and becomes show control.
- MIDI cues trigger lighting desks, hardware samplers, anything with a MIDI in.
- OSC cues talk to TouchDesigner, Resolume, Isadora, Max, Ableton, MadMapper — essentially everything in this field speaks OSC.
- Network cues hit other QLab machines, so a multi-room installation can run from one master.
The pattern to know: QLab as the conductor, your visual software as the instrument. Let QLab own the sequence and timing, and let TouchDesigner or Resolume do the rendering. Both are better at their own job, and when something breaks you know which half to look at.
Habits that save shows
- Always have a panic cue. A Stop All / blackout cue at a memorable number. You will need it.
- Label everything. “Cue 240” means nothing at 11pm. “House to half” does.
- Use a separate cue list for checks — audio device test, projector wake, level check — and run it before every show.
- Never trust hardware to stay put. Audio device assignments and display arrangements change when things get unplugged. Re-verify on the actual rig.
- Save versions.
show_v1,show_v2. QLab workspaces do get corrupted. - Test the whole thing cold. Quit, reopen, run from cue one. A show that only works from a warm session isn’t a show.
Where to go next
For gallery work, look at triggers — hotkeys, MIDI in, timecode, and in the paid tiers timecode sync and more — so a sensor or a button can fire a cue instead of a person. Combine that with an auto-following sequence and you have an installation that responds to a visitor and then resets itself.
The licensing to know: QLab’s basic audio features are free; video, lighting, networking and timecode features sit behind Pro tiers, available as rentals by the day as well as permanent licences. Day rentals are how most small productions handle a short run.