Parallel compression is often referred to as a go-to technique for mixing and mastering.
The term seems to have been coined by Bob Katz, a renowned American audio engineer specializing in mastering, known for his excellent book Mastering Audio: The Art and the Science.
In itself, the mixing method has existed since at least the late 1970s. It was initially used by many New York studios, which gave it its other name, New York Compression.
But concretely, what is it about? In what situations can this audio compression technique be used, and for what effect? And above all, what are the ideal settings for parallel compression?
The answers are in this article! 🙂
The Principle of Parallel Compression
Parallel compression is a fairly simple yet very effective technique, applicable in many situations — both in mixing and mastering contexts.
A Simple Technique
It involves taking a track (or a bus) and duplicating the signal to obtain two identical tracks.
On the second track, we apply compression affecting the entire signal, not just the peaks. This second track is then mixed more or less subtly with the first.
Here is a diagram summarizing this concept:
Note that in this idea, a number of audio compressors (plugins) have a setting called Mix or Blend, which allows mixing the original signal with the compressed signal.
This means that these plugins can natively generate parallel compression without the need to duplicate the track.
Note: I mentioned earlier about “duplicating” the tracks to simplify the explanation. However, it is also possible in most DAWs to send the raw signal from one track to another without having to copy the content.
What is the Goal?
With parallel compression, the original track remains intact. We do not touch the transients — their attack is therefore preserved.
However, thanks to the compressed track, we can bring out the quieter sounds, which will result in increased body and power, while limiting the loss of dynamics. It’s as if we only kept the benefits of compression.
And this is the whole difference with classic compression!
If we had compressed the first track directly, the peaks would also have been attenuated, and we would have lost significantly in attack and dynamics.
With parallel compression, on the contrary, we hear both:
- the uncompressed, dynamic, and natural sound of the first track;
- the compressed sound of the second, but as if it only affected the quieter sounds, which are then raised in volume.
Result: the mix sounds louder but remains pleasant.
When to Use This Method?
As I mentioned earlier, this technique can be used in many mixing situations:
- For mastering — probably the best time to use parallel compression, which then helps bring cohesion to the mix.
- On drums — parallel compression proves to be very effective on all drum, percussion, or electronic beat buses.
- Other Uses — of course, it can also be applied to a vocal track, a bass, or even a piano to increase sustain.
However, be careful not to overdo it, as it may distort the piece…
The Settings
The settings to apply for parallel compression are very simple and especially quick to perform. Whether your DAW is Ableton Live, Cubase, or even FL Studio, these settings will always be the same.
First of all, you need to set the threshold or threshold to a very low value, depending on your input signal. The idea is that almost all of this signal should be compressed. If you set it too high, only the peaks of the signal will be affected, and parallel compression will be less effective.
The attack should be as fast as possible, so that the transients are fully crushed, since it is mainly the quieter sounds that we are interested in here (and not the transients).
The release, on the other hand, should be set to a medium value. You can start with around 200 milliseconds (ms), adjusting according to your tastes and the sound you are looking for, but not necessarily in relation to the tempo.
Note that a release setting that is too fast will give a compression effect that is too obvious, likely presenting many audio artifacts (the