sidechain compression

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068 | COMPUTER MUSIC JULY 2005 TUTORIAL make music now Sidechaining Sidechain reaction So many techniques, so little time. Here's one less to worry about as we demystify the art of sidechaining C omputer music can be something of a technological bulldozer – powering forwards, razing old technology to the ground as it goes. The shift from analogue to digital has been swift and decisive but, in most cases, the positive aspects of the analogue studio have been migrated to the virtual one. Countless plug-ins are available these days, and they can perform just about any task that a piece of studio hardware can. It’s all about the sound, though, and in the endless quest to get the sought-after analogue sound in software, developers have employed increasingly clever techniques to emulate real-world bits of kit – especially the rare and expensive ones. Such attention to detail continues to improve the quality and flexibility of the tools we have to work with. But you have to understand what a feature’s for in order to be able to use it. In this tutorial, we’re going to take a look at sidechaining and its different uses. Sidechains or Key Ins are found on pretty much any hardware dynamics processor worth its salt. They’re a means of controlling the processor using an external audio source, and they can be used in numerous ways. To make life easier for us, plug-in developers sometimes incorporate automated sidechain functions, while others provide true simulations of the hardware sidechain. Here we’re going to look at how you can make use of the latter. We’ll start by showing you how to route audio to the sidechain and go on to describe some of the different engineering techniques and effects that can be produced once you’ve done it. We’ll also look at the operation and routing configuration behind the technology, guide you step-by-step through four classic sidechaining techniques, and point you in the direction of a few good plug-ins with dedicated sidechains. cm On the DVD TUTORIAL FILES To hear some examples of these techniques in action, head to the Tutorial Files folder of the DVD-ROM

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Page 1: Sidechain Compression

068 | COMPUTER MUSIC JULY 2005 TUTORIAL

make music now Sidechaining

Sidechain reactionSo many techniques, so little time. Here's one less to worry about as we demystify the art of sidechaining

Computer music can be something of a technological bulldozer – powering forwards, razing old

technology to the ground as it goes. The shift from analogue to digital

has been swift and decisive but, in most cases, the positive aspects of the analogue studio have been migrated to the virtual one.

Countless plug-ins are available these days, and they can perform just about any task that a piece of studio hardware can. It’s all about the sound, though, and in the endless quest to get the sought-after analogue sound in software, developers have employed increasingly clever techniques to

emulate real-world bits of kit – especially the rare and expensive ones.

Such attention to detail continues to improve the quality and flexibility of the tools we have to work with. But you have to understand what a feature’s for in order to be able to use it.

In this tutorial, we’re going to take a look at sidechaining and its different uses. Sidechains or Key Ins are found on pretty much any hardware dynamics processor worth its salt. They’re a means of controlling the processor using an external audio source, and they can be used in numerous ways.

To make life easier for us, plug-in developers sometimes incorporate

automated sidechain functions, while others provide true simulations of the hardware sidechain.

Here we’re going to look at how you can make use of the latter. We’ll start by showing you how to route audio to the sidechain and go on to describe some of the different engineering techniques and effects that can be produced once you’ve done it.

We’ll also look at the operation and routing configuration behind the technology, guide you step-by-step through four classic sidechaining techniques, and point you in the direction of a few good plug-ins with dedicated sidechains. cm

On the DVDTUTORIAL FILESTo hear some examples of these techniques in action, head to the Tutorial Files folder of the DVD-ROM

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Page 2: Sidechain Compression

TUTORIAL JULY 2005 COMPUTER MUSIC | 069

Q&A focusmake music nowSidechaining

The ins and outs of the sidechainHow it works

S idechains can be found on both compressor/limiters and gates. Developed in the days of purely

analogue processing, sidechain circuitry allows you to control the behaviour of a dynamics processor.

Two different audio sources are sent to the processor. One is the audio on which the processor is going to operate – this goes to the input. The other is the

signal that determines when (and sometimes how) the processor operates on the input audio – this is applied to the sidechain return and may originate from the sidechain send.

The sidechain signal can either be a processed copy of the input signal originating from the sidechain return (true sidechaining) or can originate from a completely different source. Which

you choose depends on the effect you want to create.

To create frequency-dependent compression – by patching an EQ unit into the sidechain – a copy of the input signal must be used. This is a technique employed to reduce sibilance in vocals.

However, when it comes to ducking and creative gating techniques, completely different audio sources must

The Waves C1 provides compression and gating. The plug-in is capable of applying two frequency-selective processes simultaneously and features a sidechain listen button.www.waves.com

Waves C1 $200

Part of the new MClass mastering suite, the MClass Compressor differs from others by providing a

true sidechain input, giving you complete control over what signal you use.www.propellerheads.se

Reason MClass CompressorPropellerheads Reason 3.0 £329

Shipping as part of Apple’s Logic, this is one of very gate plug-ins around that comes with a sidechain (courtesy of Logic’s general architecture). It’s also very easy to use.www.apple.com

Apple Logic Pro Gate Apple Logic Pro 7 £699

INPUT

DYNAMICS PROCESSING

OUTPUT

SEND RETURN

Four sidechaining plug-ins

Kjaerhus’ Golden Uni Pressor is the latest addition to their Golden range of plug-ins. The sidechain has low- and high-pass filters for frequency selection, and a listen button.www.kjaerhusaudio.com

Kjaerhus GUP-1 $88

EQ (OR OTHER

INSERT)

It’s really quite simple. The audio is first of all sent into the dynamics processor. Then, before the signal is processed in any way, it’s split into two. One branch goes on to be processed and the other is routed to the sidechain send. The

sidechain return is linked directly into the dynamics processing unit. By inserting some means of processing into the sidechain, it’s possible to manipulate the way in which the compressor responds.See, we told you it was easy!

So how does a sidechain work then?

be used. We’ll be looking at all of these methods in more detail a little later on in this tutorial.

Sidechaining is a fairly advanced engineering technique. It’s also a bit of an effort to program, and consequently many plug-in developers omit such functionality. However, there are still several options available to us, a few of which are shown below.

CMU88.t_side 069 27/5/05 2:30:04 pm

Page 3: Sidechain Compression

070 | COMPUTER MUSIC JULY 2005 TUTORIAL

make music now Sidechaining

Two of the most useful applications you’ll find for compressor sidechains are

ducking and de-essing. Ducking involves dropping the level

of one signal to allow another to be heard more clearly. The most common use is to help a kick drum cut through a heavy bassline that’s masking it. By running the bassline through the compressor and using a copy of the kick drum track to trigger the

compression via the sidechain, the bassline is compressed every time the kick drum sounds. Not only does this allow the kick drum to break through and be heard, but it also helps meld the two together.

Another popular use for ducking is in voice-overs, dropping the level of background music whenever the speaker begins to talk.

De-essing (the process of reducing the level of sibilant sounds in a vocal)

can be described as frequency-dependent compression. By sending a copy of the input signal through an EQ unit into the sidechain return, the compressor can be triggered by specific frequencies in the signal. For vocals, this range is between around 2-8kHz.

The EQ unit is used to exaggerate the offending frequencies so that when they occur the compression is triggered. It’s also useful for cutting frequencies that you don’t want to compress.

Compressor sidechains can be used for both creative and purely practical effects. Here’s how…

Compression sidechaining

3 Turn the S1 send amount on the kick drum channel fully up. Set the compressor to a fairly high Ratio (we’ve gone for infinity to illustrate the effect) and a low

Threshold. Use a fast Attack and a relatively quick Release. Hit play and alternate between bypassing and activating the compressor to hear the effect.

2 Patch the output from the synth into the input of the compressor, and the output of the compressor into an audio channel in the mixer. Connect the main outputs

from the drum machine to a channel in the mixer and Send Out 1 to the Sidechain In on the Compressor. >>

1We’re using Reason. We’ve created a ReDrum to provide the drums, a Subtractor synth for the bassline, and the new MClass compressor. We’ve programmed a four-to-

the-floor kick drum into ReDrum and a sustained bass note into Subtractor, using the Bd_Blockrock Kick and Mitsubishi bass patches, respectively. >>

STEP BY STEP Ducking

3 Turn the auxiliary 1 send level on the sampler’s mixer channel up to full. Using the EQ, create a peak in the 2-8kHz frequency range. Set the compressor to a

medium Ratio and fast Attack and Release. The sibilance should now be less pronounced.

2 Connect the output of the sampler to the input of the compressor, and the output of the compressor to an audio channel on the mixer. Connect the first auxiliary

send from the mixer to the EQ input, and the EQ output to the sidechain input on the compressor. >>

1 Create an NN-XT sampler, an MClass compressor and a PEQ-2 parametric EQ. Load a vocal sample containing plenty of sibilant sounds into the sampler. If you don't

have one to hand, we’ve included one on the cover DVD for you to use. >>

STEP BY STEP De-essing

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Page 4: Sidechain Compression

TUTORIAL JULY 2005 COMPUTER MUSIC | 071

Q&A focusmake music nowSidechaining

Gate plug-ins with sidechain functionality are harder to come by than their compressor

counterparts, but they do exist and can be put to great use.

Gate sidechains operate in the same way as those in compressors. The signal to be gated is applied to the processor’s input, and the signal controlling when the gating occurs is applied to the sidechain.

Of the several uses for sidechaining

gates, one of the most handy is for tightening up the timing of instruments to align with drum tracks. The classic example is when a bassist’s playing is slightly premature, which can easily be fixed using a sidechained gate.

By feeding the bass through the gate and a copy of the drums through the sidechain, the gate can be set up to open only when the drums play. By inserting an EQ into the sidechain path, or using sidechain filters, the response

can be tuned to a particular drum – most often the kick. This technique can also be used to revitalise basslines.

Aside from corrective engineering, there are some more creative uses for gate sidechains too. Excellent staccato pad effects can be achieved by feeding a long sustained sound through the gate and a rhythmic sound through the sidechain. This doesn’t have to be the drums from the track but those are obviously a good place to start.

Shut the door on unruly drums and open the gate to perfect pads with these effective gating techniques

Creative gating with sidechains

3 The final stage is to adjust the attack and release parameters so that the pad sounds the way we want. The best way to do this is to hit play and experiment.

It’s possible to create a similar effect by cutting up the loop, however you don’t get the same control over the envelope functions as you do when using a gate.

2We’ve inserted a gate into the synth channel and assigned the hi-hat to its sidechain input (by calling up the above menu from the Sidechain button at the top

right of the gate’s interface). Then we’ve muted the hi-hat at the mixer. Don’t mute the hi-hat track in the arrange page, as this will kill the input to the sidechain. >>

1We’ve opened Logic Pro’s ES2 synth, selected the Dark Pad preset and drawn in a long note. Next we’ve imported a hi-hat loop, which we’re going to use to

open and close a gate on the synth. >>

STEP BY STEP Gating a pad sound

3We’ve created a new audio track and copied the drums onto it. Using the scissors tool we’ve isolated all of the kick drum hits and then routed this new kicks-only

channel to the sidechain instead of the original drum track. We’ve muted the audio on the kick track and set the A, H and R values of the gate to get the sound we want.

2We’ve inserted a gate onto the bassline channel and routed the drums to its sidechain. Using the sidechain filters, we’re going to isolate the kick drum. By clicking

on the Monitor button we can listen to the sidechain input. But there’s a problem, we can’t isolate the kick from the snare – so we’ll take a different tack. >>

1 To begin with, in Logic Pro 7 we have a drum track – comprising kick, snare and hi-hats – and rather a busy bassline. What we want to do is sidechain the gate so

that it only opens when the kick drum is played – effectively creating a new bassline from our original one. >>

STEP BY STEP Tightening a loose groove

CMU88.t_side 071 27/5/05 2:30:18 pm