Gate Effects
By Julian Colbeck

Noise

When you hear the words 'gate effects' or 'gates,' what people are talking about - even if they don't know they're talking about it - is a noise gate.

A noise gate is a piece of studio equipment whose primary purpose, you won't be too shocked to discover, given its name, is to remove unwanted noise from a piece of audio material. It's an electronic switch that mutes a signal falling below a certain level to 'gate out' unwanted noise.

Say you have a nice recording of an acoustic guitar, but, in the background there's some noise (squeaks, the player shuffling around a bit...). Well, you can apply a noise gate to the track, and set the threshold at a level that when the main signal (i.e. the guitar playing) drops below a certain level the gate slams shut. Bingo. You won't hear any of that unwanted background noise in the gaps between your guitar playing.

Effects

Aside from other controls for altering sensitivity, envelope etc, noise gates can be used for other purposes like gluing a sloppy bass part to a kick drum, or gluing a sine wave oscillator to an 808 kick to generate deep bass. Noise gates can also be used as effects generators using the so-named side-chain feature.

Instead of the threshold being set manually, this cunning feature 'opens' and 'closes' the gate automatically depending upon another audio signal that's been patched into the side-chain input. If that audio signal is something like drum machine pattern (i.e. lots of short, dynamic bursts of signal) then that rhythm will be applied to the main audio track on which you are using the noise gate.

In place of your acoustic guitar, let's take a synth pad, or some backing vocal 'Oohs.' If you apply a noise gate with side-chain inputted drum beat on this type of sound - i.e. a smooth, sustained audio signal - it'll turn it into a sort of groovy, stuttering effect in the exact same rhythm as the drum beat. In effect the drum beat will 'play' the synth or vocal.

This effect is extremely infectious, creating instant danceability, instant feel, instant but non-intrusive movement, not the least because it is precisely in-time with the drum beat, and so, we hope, with the rest of your track.

Style

Producers have been using this trick for years; ever since the disco boom in the mid seventies. The great thing about a gate effect is that it doesn't impose a stylistic slant on a track. It can be a subtle addition, working like an occasional timed delay as on Madonna's Vogue, or it can be an intrinsic scene-setter as in the opening of Seal's Crazy. It can generate swing on a hard rock song, or be the basis for an entire trance set.

However, using a 'real' noise gate isn't exactly problem free for those of us on a less than spectacular studio budget. First you have to buy a noise gate or noise gate plug-in. Then you've got to be able to understand and operate these fairly sensitive pieces of equipment. If you tie up your noise gate for a gate effect then you won't be able to use it as, well, a genuine noise gate (you'll have to record one of the effects first, then unplug, replug etc.) And as for plug-ins, DSP is always going to be an issue in terms of the potential draw on your processor.

MIDI

So in 1994, shortly after the first Twiddly.Bits disk rolled out of production, Keyfax Software came up with the idea of creating a MIDI gate effect disk, which was inexpensive, a cinch to set up, and enabled people to use multiple/simultaneous gates. Needless to say it was an instant success and remains in production to this day.

MIDI is tailor made for this type of purpose. Essentially a noise gate either lets a signal pass (Full on=127) or shuts it off completely (Off=0). By creating rhythmic patterns using lots of 127 and 0 value volume control messages, you can so replicate the exact same effect as does a side-chain/drum machine-connected noise gate.

Moreover you can get more sophisticated by 'half opening' the gate (volume value of 34 or 64), plus you can apply the rhythms to modulation, pan, filter controllers. Or you can create massively complex effects by combining two or more gate patterns to the same sound, or using the same gate pattern on five different sounds. The possibilities are completely endless.

Keyfax' s Gate FX

This product, which can be downloaded in the shop or purchased on disk, comprises a series of 4-bar tracks within a SMF .mid file. Each track contains different controller data and so produces a different gate effect. Using MIDI gates is as simple as using the same playback MIDI channel for both gate effect and part (again, sustained synth pads and vocal sounds work best). You can then simply copy and paste the gate for as long as you want the effect to continue.... 100 bars, 16 bars, for 1 bar every 4 bars, even cutting and pasting between different gates to produce completely new patterns.... it's entirely flexible.

Opening the gates

Several other companies now produce MIDI gates. It is also, to be fair, not that difficult to create your own patterns without having to spend any money at all. Gate FX is simply a great starting off point to see how it's done.

In 2002 Keyfax revamped its popular Gate FX disk for the Yamaha Motif, producing Mo'Gates in native Motif Pattern format, building on the original disk with additional filter and 'bass tweak' patterns. Gate FX has now been re-launched as Gate FX 2002, containing the new beats and effects created for Mo'Gates in regular SMF .mid format.

The original Gate FX collection used MIDI Controller # 7 (Volume) as the vehicle for delivering on/off messages. But in fact Controller # 11 (Expression) can be a more sophisticated option, allowing you to set a basic level using Volume and controlling the internal fluctuations with Expression. Both Mo'Gates and Gate FX 2002 now offer all their patterns in a choice of Volume or Expression controllers.

Click here to view the Gate FX library.