Jack normalling (not to be confused with Jack Normalling, Chicago Cubs utility infielder, 1952-61, .267 LBA) is a feature found on almost every mixer, keyboard, and effects device.
— Mackie 1202-VLZ owner's manual, 1997
Jack normalling is essentially having a hidden default connection made inside a device, that you can still override by plugging a cable into the jack.
A Patchbay is essentially an array of jacks, at both the front and back. By plugging in all your equipment at the back, you can change what's connected to what else much more conveniently, using short cables at the front.
Most of the time, however, you likely want to maintain a standard set of connections. Sure, you want to be able to easily patch anything into track one of your Alesis ADAT, for instance, but most of the time you just want to patch in your DX100.
Normalling simplifies this, getting rid of the clutter of unnecessary cables. In most patchbays, each column is normalled so that by default, each output on the top row is connected to its neighbouring input on the bottom row. This provides a handy default path that you only need to override on rare occasions. Much tidier.
With a regular, fully normalled pair of jacks, inserting a plug into either jack will break their internal connection. So you can reroute the output somewhere else, or reroute something else to the input, or both, and the internal connection is completely bypassed.
With a half normalled pair of jacks, you can reroute the output somewhere else, and it will still go to its normal internal destination as well. You're not redirecting the signal, so much as tapping it — essentially, copying it.
You can still bypass the internal connection by routing something else to the input. Due to how electricity works, it's somewhat dangerous to try to directly combine multiple outputs together. They should only be combined indirectly, using a mixer. Patchbay manufacturers therefore ensure that inserting something into the lower jack will always safely break the internal connection. This is a good reason to stick with the convention of using the top row for outputs and the bottom row for inputs.
Some patchbays are fully normalled; some are half normalled; some aren't normalled at all; and some have switches letting you choose the normalling per channel.
In a modular synthesiser, within a single module, jacks can be normalled for convenience.
For example, the System 35's CP35 module lets you attenuate up to four different signals, and through normalling together all the inputs, lets you attenuate the same single signal by four different amounts to then send to four different places, or any other combination in between.
The System-100M's 132 module lets you mix together any four signals, and by normalling two of the channels to +10 V and -10 V, also lets you DC offset (bias) up to three signals.
A semi-modular synthesiser is essentially like a modular synthesiser of a set configuration, allowing the manufacturer to add normalling not just within each module but also connecting together multiple modules. In a fully modular synthesiser, inter-module normalling can only be achieved via the system bus or trunk lines.
For example, say you have a modular synthesiser featuring an oscillator with a CV pitch input phone jack. Sure, sometimes you want to sweep the pitch down for drums, but most of the time you simply want to relay the keyboard's pitch to it. Recognising this, the synthesiser manufacturer decides that the keyboard's CV pitch should be sent to the system bus, which can relay the value to any module that cares to listen; and that the oscillator's CV pitch input jack should be normalled to the bus's CV pitch. You can still override it by using the jack, but if the jack's empty, there's a hidden connection from the bus to the oscillator. Much more convenient. The only caveat is that clear, thoughtful labelling is required to show what's connected to what.
And this is arguably an advantage of the 2600 and System-700 over Moog's 900 Series: even though Moog's modular systems also have plenty of internal trunk lines that are either normalled to various modules, or can be connected to them via handy switches, the layout is clearer on the rival systems. While good engineering is important, so is clear graphic design. A good feature is only useful if people can easily find and use it.
- "Patchbays" Hugh Robjohns, Sound On Sound, Dec 1999
- "Studio Installation Workshop: Patchbays" Mallory Nicholls, Sound On Sound, Feb 2003
- "Patchbays in the Modern Studio" Hugh Robjohns, Sound On Sound, Dec 2020