On a VCA console, no audio passes through the fader at all, because the fader only makes a DC voltage that the automation computer reads. The strip you're holding is a remote control.
That detail explains why two very different things keep getting mixed up. A snapshot captures the state of the desk at one instant. Automation keeps a moving record of every fader move across the whole four minutes.
Both are useful, and neither replaces the other. An analog desk that stores a full snapshot is answering a completely different question from the one automation answers.
Moving-fader systems work the older way and route the signal through the fader itself. The payoff is that fader position always corresponds to the real gain of the channel, so what you see matches what you hear.
VCA desks give that up. During playback, the faders sit still while levels shift underneath them, which is why those consoles need screens or small LED match indicators to tell you whether your hand is anywhere near the level the computer is currently holding.
Moving faders carry their own costs. They make mechanical noise, which is a problem if the desk sits anywhere near an open microphone, and the fader wears out over time in exactly the way any manual control does.
Snapshots sit outside that argument entirely. Their job is the instant change, dropping a whole set of parameters into new positions at once rather than easing anything anywhere. That's why they earn their keep on complicated arrangements where six things have to move on the same beat.
VCA automation had already been running before that, with the moves written onto a couple of spare tracks of the tape machine. It worked. The faders just never moved, so you had no way to see the mix you had built.
By 1979, the Neve 8108 was combining analog and digital control with assignable functions and memory faders. SSL's 4000 B had landed in 1976, with the E following in 1979, and Bohemian Rhapsody, mixed in 1975, gets named by its producer as one of the earliest records automated at all.
Recall showed up later and solved a separate problem. Total Recall arrived in 1981 and took a snapshot of switch and knob positions rather than movements, and resetting a 48-channel desk from that snapshot still took two or three hours of manual work.
So the two capabilities grew up roughly four years apart, out of different frustrations. Automation existed because one pair of hands could not ride twenty-four faders at once. Recall existed because the next client was booked in for Tuesday and the desk had to become somebody else's desk overnight.
Touch plays that same data back but lets you move a control and write over it while you hold on. Let go, and the parameter falls straight back onto whatever automation was already sitting there.
Latch behaves identically while your hand is on the fader, then diverges at the release. The new value stays put and replaces the existing automation from that point onward, which is either exactly what you wanted or a small disaster, depending on whether you meant to let go.
Write is the blunt instrument. It erases existing data as the playhead crosses it, recording your movement, or wiping the pass clean if you sit there and do nothing.
Trim overwrites nothing. It offsets what's already written, lifting or dropping the whole curve while keeping its shape, which is the mode you want when the ride is right but the level sits three decibels low. Relative takes that further and holds a second curve alongside the first, leaving both editable.
None of those modes has any meaning inside a snapshot. A recall system stores one set of numbers and puts them back where they were. It has nothing whatsoever to say about what your hand did at bar 47.
That detail explains why two very different things keep getting mixed up. A snapshot captures the state of the desk at one instant. Automation keeps a moving record of every fader move across the whole four minutes.
Both are useful, and neither replaces the other. An analog desk that stores a full snapshot is answering a completely different question from the one automation answers.
The fader you touch is often not in the audio path
In a VCA system, the fader generates a control voltage, and a voltage-controlled amplifier elsewhere in the channel does the actual gain change. The audio never goes near the thing under your finger.Moving-fader systems work the older way and route the signal through the fader itself. The payoff is that fader position always corresponds to the real gain of the channel, so what you see matches what you hear.
VCA desks give that up. During playback, the faders sit still while levels shift underneath them, which is why those consoles need screens or small LED match indicators to tell you whether your hand is anywhere near the level the computer is currently holding.
Moving faders carry their own costs. They make mechanical noise, which is a problem if the desk sits anywhere near an open microphone, and the fader wears out over time in exactly the way any manual control does.
Snapshots sit outside that argument entirely. Their job is the instant change, dropping a whole set of parameters into new positions at once rather than easing anything anywhere. That's why they earn their keep on complicated arrangements where six things have to move on the same beat.
Faders started moving themselves in 1977
NECAM, short for Neve Computer Assisted Mixdown, arrived that year and went into AIR Studios in London first. It stored and recalled fader movements so a mixer could build a mix in stages instead of performing the entire thing live in a single pass.VCA automation had already been running before that, with the moves written onto a couple of spare tracks of the tape machine. It worked. The faders just never moved, so you had no way to see the mix you had built.
By 1979, the Neve 8108 was combining analog and digital control with assignable functions and memory faders. SSL's 4000 B had landed in 1976, with the E following in 1979, and Bohemian Rhapsody, mixed in 1975, gets named by its producer as one of the earliest records automated at all.
Recall showed up later and solved a separate problem. Total Recall arrived in 1981 and took a snapshot of switch and knob positions rather than movements, and resetting a 48-channel desk from that snapshot still took two or three hours of manual work.
So the two capabilities grew up roughly four years apart, out of different frustrations. Automation existed because one pair of hands could not ride twenty-four faders at once. Recall existed because the next client was booked in for Tuesday and the desk had to become somebody else's desk overnight.
Touch and latch split the moment you let go
The modern automation modes are where the difference turns practical. Read plays back what's written and refuses to let you change anything by grabbing a control.Touch plays that same data back but lets you move a control and write over it while you hold on. Let go, and the parameter falls straight back onto whatever automation was already sitting there.
Latch behaves identically while your hand is on the fader, then diverges at the release. The new value stays put and replaces the existing automation from that point onward, which is either exactly what you wanted or a small disaster, depending on whether you meant to let go.
Write is the blunt instrument. It erases existing data as the playhead crosses it, recording your movement, or wiping the pass clean if you sit there and do nothing.
Trim overwrites nothing. It offsets what's already written, lifting or dropping the whole curve while keeping its shape, which is the mode you want when the ride is right but the level sits three decibels low. Relative takes that further and holds a second curve alongside the first, leaving both editable.
None of those modes has any meaning inside a snapshot. A recall system stores one set of numbers and puts them back where they were. It has nothing whatsoever to say about what your hand did at bar 47.
