Parallel compression often seems like a sort of dark magic and can be very hard to get the hang of if you don't know why you are using it or how it works. By simply learning the way it works you can shed some light on how to use it and when to use it. To start with we will go through how this technique works then we will give you some practical ways to use it in your music.
How it works
To truly understand how parallel compression works we first need to know about upward and downward compression. Downward compression is the type of compression that is most commonly used. this is the type of compression in which the louder peaks of sound are brought down in level in order to give the effect of increased overall loudness. In simple terms you turn down the peaks so that the quieter sections seem lounder. this is the most commonly use type of compression as it is simply the easiest to make and the most useful in most situations.
The next type of compression is upward compression, this works in the opposite way to downward compression. in upward compression the threshold works in the same way as downward compression but the difference is upward compression will turn up and parts of the signal that lie below the threshold. in simple terms upward compression is simply turning up the quieter parts of a signal rather than turning down the louder parts of the signal. This can be a very useful form of compression if your are wanting to increase overall perceived loudness but don't want to affect the delicate transients in the signal.
parallel compression was discovered as a way of achieving the same effect of an upward compressor by using the readily available downward compressors found in a conventional studio as upward compressors were very rare and hard to come by. so parallel compression is a great way to achieve this technique.
Parallel compression such a popular technique because it can provide such a "punchy" sound that u wont find when using any other compression technique. it is ofter used on drums to crate a sense of "punch" of thickness, or is also popularly used on vocals to give the same sense of thickness. This technique is not limited to just these uses and once you get the hang of it you will easily be able to spot when its needed and on what instruments.
image credits: https://www.soundonsound.com/techniques/parallel-compression
How to use it
So how do we achieve parallel compression? well thats quite easy really, as most of the people reading this will be working in a DAW, i will explain in these terms. So too start with you want to send the signal that you want to compress to an aux track so you have 2 separate versions of the same signal running in parallel to each other. You then want to put a compressor on this aux track, do bear in mind these days there is a huge choice of compressors which have been created for this use but any compressor that can handle fast attack and release times can be used. A popular free parallel compressor is combear which can be downloaded free of charge here:
Once you have your compressor set up on your aux track your ready to start adjusting your settings. be aware that if your these settings wont apply for a 2 knob plug in such as combear but if you are using a different plug in these are the parameters you want to look for.
So when you use parallel compression you will be looking for a very extreme compression sound meaning that you will be using all your parameters in a very extreme way.
we will start with the ratio as this is the main parameter to look at in order to achieve this heavily compressed sound. So the ratio is usually set anywhere between 8:1 and 40:1 but most commonly uses ratio's above 20:1. As with all these parameters the exact ratio you use will be dependant on the exact signal you are using this for but as a general tule of thumb 20:1 is a great place to start, then once you have all your parameters set up you we recommend you have a quick play around to see how a change in ratio can effect the sound you are wanting.
As we are looking for an extreme compression sound the threshold should be set to allow anywhere from 10db - 30db of gain reduction depending on the how extreme you want it to sound.
Attack and release:
the attack and release parameters are the part of this technique that shapes its character. so playing around with attack and release are the best way to understand what this technique does and the different characters that can be achieved with this.
To achieve the sound we want using this technique a fast attack parameter is crucial, we usually recommend 1ms - 30ms. an important thing to bear in mind is that the longer you set the attack time the more of. a "punchy" sound will be achieved, but again just have a play around with this to find where you prefer it as different engineers will use this parameter differently.
Similar to the attack the release time need to be fast to medium and we usually suggest around 20ms - 200ms. The faster you set this the more aggressive it will sound while setting a slower release will achieve a more natural compression sound so play around and find where you like it for your chosen signal.
once your parameters are set up you want to adjust the level on your aux track until you have a good mix of both the heavily compressed and uncompressed signals which will achieve this intended "punch" and "thickness"
When you start using this technique its best to try learn how to use it either on drums or vocals as these are the instruments in which it most commonly used and will be the best place to start with this technique.
Give this technique a try and let us know what u think of it using the chat box in the bottom corner. We are always happy to answer any question or give any advise as best we can, so just ask!