Tip of the Week 21: Parallel Processing

You will have heard of parallel compression, where a signal is duplicated, one version is heavily compressed and mixed with a clean version of itself. There are of course other types of parallel processing that are incredibly handy to employ in your mixing. The reason for parallel processing is to maintain the original essence of the recording while still heavily altering the sound, here are a few more examples.

One of the best sounding effects, especially for harder genres is distortion. It adds grit and harmonics to the sound making it harsher and brighter in a good way. The issue is, the harder you distort a track, the more the original information is destroyed.

For example, a lot of distortion is done by squaring off the peaks of the sound waves, essentially crushing the dynamics of the sound. It is a great effect but can really kill the movement of volume.

By mixing a clean version of the sound into a distorted version, you can still maintain a small amount of dynamic range, or more correctly, perceived dynamic range. This also means that because there is still an audible clean signal, the distorted track can be pushed much harder.

Note how the distortion (bottom) fits around the notes being played.

Perhaps side-chain the distorted track to the clean one so the distorted track gets compressed at the peaks for a very unexpected sound. Normally at the loudest parts, the sound will be even more distorted, but this way will mean the sound gets cleaner at the higher volumes.

This works well with long tailed kicks where you want a clean initial punch but some real grit in the tail.

Another trick would be to add a different effect onto the "dry" signal. For example, if you didn't want to add reverb to the distorted track, but still wanted a sense of space, you could have a distorted track mixed in with a clean track with reverb.

There are many cool ways to parallel process a track using reverb. My favourite one is to take a 100% dry signal alongside a 100% wet signal and add a compressor to the wet track. Trigger the compressor with the dry signal and set the threshold very low with a gentle knee. This will mean the reverb morphs and pumps around the dry signal.

Add a brickwall limiter onto that signal and you get a heavily processed sounding result where it feels like the room and reverberations are constantly fluctuating and taking control.

Employing these can be great, one way to use them is to parallel process with them. Apply the effect to each of the track but slightly offset the timing of the effect so it either goes at a different speed or initiates from a different part of the cycle.

Buttons such as "spread", if available, do the same process 

Hard pan each track left and right and you suddenly have a wider stereo spread. This is actually built into a lot of the plugins already so there's a good chance you just need to select the stereo option however is a very useful trick if you are stuck with a mono only plugin.