Sometimes nothing sounds better than a compressor beating the crap out of a drum track. Get the attack and release settings right, the kick and snare pump in time, and it can sound massive. Other times, the result will sound skinny and feeble, and you’ll wish that there was some way you could have all the goodness of the compressed sound that everybody loves and yet still retain some of the dynamics and detail that characterised the original unprocessed sound. Naturally at first you try backing off the compression a little, but then you find that it’s not giving you the drive and power that you were after. So it seems that you’ll have to compromise, and make a choice between the powerful and driving sound that your favourite compressor offers, or the detail and clarity that you find in the unprocessed sound.
But what’s that you say? I can have both at the same time? That I can have all the character and punch from my favourite vintage compressor set to stun, and yet simultaneously retain all the dynamics and detail from the original signal? This is pretty much what parallel compression offers. It’s a miracle!
As some guy in a movie once said, we can do this the easy way, or the real easy way. I think he was making a threat, but me, I’m just talking about using parallel compression on some audio. Here’s the real easy way: choose a compressor with a Mix or a Blend knob. In the world of hardware, the Focusrite ISA220 channel strip is just such a device. Actually, in this case the ISA220 has just a Blend button, not a knob - you don’t actually have any control over the blend, although the default setting, with the compressed signal dropped by 6dB to compensate, is perfectly sensible. I’ll assume, though, that like most visitors to this site you’ll be doing your signal processing using software – and here you also have plenty of options for real easy parallel compression. Software such as the UAD Precision Compressor, Voxengo Marquis or Crunchessor, or PSP MasterComp, each has a dedicated Mix control.
So, just what are we Blending or Mixing? Why, the compressed signal with the original, of course! It makes perfect sense: we compress the sound as much as we want to, reducing the dynamic range and getting all the punch and character that we desire. In doing so, however, we’ve lost much of the transient detail and high-frequency content that make the source sound polished and expensive. Therefore, we mix or blend back in a little of the original signal to give us back those elements that we’ve lost. The result is the best of both worlds: all the taste and none of the calories. But is this any different from simply compressing a bit less? Yes, the results can be very different. Try it; you’ll probably notice the greater crispness in the high frequencies immediately.
With the real easy way to parallel compression, we just turn the mix knob to decide how much of the original signal to blend in. And because the uncompressed signal is there, preserving the transients and dynamic goodness, we can usually drive the compressed part even harder than normal.
But you said I could have all the punch and character from my favourite compressor? And my favourite compressor doesn’t have a mix or blend knob – so what happens then? Well, here we have to move from the real easy way to the plain old easy way. Assuming your favourite compressor is a software VST, and your sequencer of choice has PDC (Plug-in Delay Compensation – pretty much every modern software sequencer has this nowadays) you’ll just need to insert your compressor on a Group or FX channel, and treat it as a Send effect rather than an Insert. Here I’m using Cubase 4; the steps will vary slightly with other sequencers, but any modern sequencer will be able to do this.
Firstly, set the Send output from your drums, or other instrument track, to Pre rather than Post – this is so that you’ll be able to adjust the volume of the uncompressed drums whenever you want without it affecting how much signal it sends to the Compressor. Then drop the fader on the uncompressed signal so that all you can hear is the sent signal running through the compressor.
Adjust the volume of the sent signal so that it is an appropriate volume at the compressor (eg. nice and strong, but in no danger of clipping). Then manipulate the compressor controls in the usual way to get the sound that you want. Remember that you’re going to be restoring some of the dynamics and transients later, so you can probably be a bit more heavy-handed than you would normally be with traditional compression.
Next, raise the fader of the uncompressed track until you like the combined sound. If the combined sound is too loud and clips the output channel, lower the fader of the compressed track and the uncompressed track and rebalance.
When you have a combination which has the desired ratio of compression effect to dynamics and transient detail, group or link the two channels together, so that you can just use the one fader to control the overall volume of the instrument you have been working on.
That’s it – you’re done.
Drums are, in my opinion, the most obvious source to benefit from this process, but you can use it anywhere. It can be addictive, so don’t forget that most things sound fine with just a bit of regular compression. But on drums it can be very beneficial – or anything where both detail and punch are to be valued. And don’t forget the stereo buss too! It’s a great way to compress your final mix without crushing the life out of it.