Two schools of recording cues, where value tracking came from, what block cues are for and how to tell which scheme your show needs.
Take a play with two hundred cues. Cue 5 sets the backlight — blue, cold, and it lives through the whole first act. At the hundredth run the director says: "make it warmer".
How many cues will you have to rewrite?
The answer depends on which school your console belongs to. And this is not a question of convenience — these are two different ideas of what a cue actually is.
Every cue holds the entire picture. All 512 channels of the universe, every fixture, all at once. Press GO and the stage becomes exactly what was recorded.
That is honest, predictable and obvious at a glance. No magic: what was recorded is what you see. At a concert, where every song is its own look and the next has nothing in common with it, nothing better is needed.
But back to our backlight. It sits in cue 5 and is physically written into all forty following cues — simply because each of them holds a full picture, and in each of them that channel holds blue. Change the colour and you edit forty cues. One at a time.
A cue holds only what changed. Everything it doesn't touch keeps living from the previous cues — it "tracks" forward down the list.
The backlight from cue 5 is recorded exactly once. Cues 6 to 45 know nothing about it and don't want to: it simply stays on, because nobody touched it. Change the colour in cue 5 and it changes to the end of the act.
This is how theatre consoles worked back when memory was measured in kilobytes and storing a full snapshot for each of two hundred cues was physically impossible. The saving stopped being an argument long ago; the habit stayed, because it turned out to be useful.
There is a side gift too: cues become readable. The list shows "12 channels touched here" instead of "the whole stage again". From that number you understand in a second what the cue does.
An edit at the top of the list arrives at the bottom. The whole list. Including act two, where the same fixtures are doing something completely different.
The classic situation: you changed the wash in the third scene — and found it in the finale, where it had tracked through eighty cues nobody touched.
That is why every cue has a Block button. A block cue stops tracking: state is computed afresh from it, and the past doesn't seep in.
The practice is simple: put a block at the start of every scene. Then edits inside one scene stay inside it, and scenes stop affecting each other. Worth making a habit immediately, rather than after the first surprise.
Recording is measured against the tracked state. When you re-record a cue, it compares the stage not against nothing but against what would have arrived here without it. That is why "record" in tracking gives you a cue of twelve channels rather than five hundred.
A channel absent from the state counts as zero. Otherwise every cue would drag a whole universe of zeros — and tracking would be identical to snapshots under a different name.
Killing a channel is a change. It was 255, now it is 0 — the zero is written explicitly. Otherwise you could never turn a fixture off in tracking: its value would simply track onwards.
And the thing most often broken in home-grown implementations: GO applies the entire resolved state — the merge from the last block cue to here, not just the contents of this cue. Apply only the contents and GO would kill everything the cue doesn't touch, turning tracking into a strobe.
Ask yourself whether light in your show lives longer than one cue.
Concert: every song is its own look, blackout between songs. Light does not outlive a cue. Use snapshots: simpler, safer, nothing to track.
Play: general cover stands through the whole act, accents change. Light lives a long time. Use tracking: it will save you an evening of work on every edit, and not just once.
In Flux Lights the Tracking switch is a property of a particular cue list, not of the application. The same show file can hold a tracked list for the play and a snapshot list for the curtain call. Existing shows are unaffected: they keep running as snapshots until you say otherwise.
Honestly, so you don't discover it during a get-in:
All three belong to the same family as tracking itself, and large theatre consoles have them. We know about them and they are on the list.