Compressors can be a great way to even out the dynamics of a drum mix, vocal performance or any audio signal. A compressor works by lowering the gain when the signal jumps above a certain level or threshold. This in turn makes the quieter elements appear to be louder and raises the overall perceived level. Most often the impression is that it "fattens" the sound. If the signal is heavily, or "overly-" compressed, this can result in the dynamic range of the signal being squashed.
Parallel Compression, also known as New York Compression, is a way of beefing up the sound and retaining the dynamic range of the original signal. It works by mixing the dry (or lightly compressed) signal with a heavily compressed version of the signal. Although infamous due to it's use on drums, this technique can be used for any instrument in any virtually any musical genre with great results. In fact, it's a technique that, whilst commonly applied in the Mixing stage, can even be used when Mastering a track to give it more presence.
In this tutorial we'll explore how to apply parallel compression using the Bus Send technique in Logic Pro, but you can follow along in Logic Express or any DAW of your choice.
01 - Relative Levels
I'm using four tracks of drum and percussive loops in a four bar loop in this example.
First and foremost you need to mix your tracks until you are happy with their relative volume levels. You can do this in Logic's Mixer more easily than in the Arrange area.
I've also slapped an Adlimiter on the Stereo Output channel strip. This is entirely optional!!
Here's what the loop sounds like "dry":
02 - Group the "dry" Drums
We're going to route the entire signal from the 4 channel strips via a Bus to a new Aux Channel Strip. In the Mixer swipe over the bottom area of the 4 channel strips to select them and click and hold on the Output slot and select any free Bus. I've chosen Bus 20.
A new Aux Channel is created with Bus 20 as the Input. The signal from all the drum channels is now being fed to Aux 1. I'll rename mine "Dry Drums".
03 - Light Compression
This step is optional. I like to add some light compression to the Dry Drums Aux to help all the elements gel together. Click and hold on the top insert slot and choose Dynamics > Compressor
Notice the Ratio and Threshold settings I've dialed in below. It creates a mild overall compressed effect.
See if you can hear the subtle difference in the mp3 sample:
04 - Sending to a Bus
In order to set up our parallel compression signal chain we need to send the dry signal to a new Aux channel strip via a Bus so we can apply heavier compression to that signal. You may wish to send from the separate drum channel strips or from the "Dry Drums" Aux channel. I'm going to send from the original separate channels.
Select all 4 channel strips and click-hold on one their empty Send slots. Select an empty Bus (I've chosen Bus 10).
Rename the new Aux channel (Input is set to Bus 10), to "Big Comp". With the four drum channel strips still selected, Option-click on one of the selected Send knobs to set them all to 0dB.
Playing back your project will reveal that you've increased the volume level of the drum sound.
05 - Heavy Compression Settings
Insert a Compressor plugin on the first insert slot of the "Big Comp" Aux channel strip. Here is where you can now let rip with a higher than normal ratio amongst other settings to give your drum loop a fuller, bigger sound. My settings are pretty extreme and the resulting sound is squashed and over-compressed. But that's a good thing for when we come to mixing this with the dry signal!
Experiment with the Ratio, Attack and Release and try the different Compressor Circuit types too.
I've solo-ed the "Big Comp" channel strip and here is what the heavy compression sounds like all by itself:
06 - Going Parallel
Un-solo the "Big Comp" channel strip and lower the level of the Aux Channel right down until you can hear only the dry drums. Now carefully increase the level fader while listening to the loop. The aim is to mix the dry and compressed signals so you can still hear the detailed dynamics of the "dry" performance while adding a fullness (and in this case, crunchiness) to the entire drum mix.
The amount of extra body you choose to add will depend very much on the instrument(s) and the genre of music you're mixing. Try A/B-ing the parallel compression by toggle muting the "Big Comp" channel strip.
Here is my final result, which I've added a subtle amount of parallel compression to.
Experiment with more pronounced compression settings on the "Big Comp" channel strip for a larger bodied feel. I'd also highly recommend checking out Olav Basoski's Electronica Workflow Tricks tutorial for more Compression, EQ, Side-chaining and Advanced Studio Production techniques.