If you're a music producer, you definitely know about compressors, you probably hear everyone and their mother talk about their favorite compressors, and you are probably using them yourself. The question is, how well do you understand what it's doing to your signal? And what else can it do that you maybe haven't explored yet? Let's dive into all that and more today.
What is a Compressor?
Let's start with the basics, what exactly is a compressor? The simplest way I can explain it is that it is a tool that reacts to the volume output of the track that it's on and automatically adjusts the volume accordingly, depending on the settings you have. It's primary use is to reduce the dynamic range of the audio signal, to make the loudest parts quieter so the whole thing is more uniform and in control. However, there is much more that this plugin is capable of.
The basic settings of a compressor are the threshold, attack, release, and ratio. The threshold is the level of the audio signal coming in that will trigger the compressor. If you set it higher, the compressor won't react to audio at a lower volume and will only trigger when it gets really loud, while at lower settings, the compressor will trigger much easier with less volume. The ratio determines how strong the compressor will reduce the volume once the threshold has been reached. 1:1 means that it isn't doing anything while 10:1 would be incredibly strong. The exact meaning of these numbers is this: for every (first number) of decibels the signal exceeds the threshold, only 1 decibel will be let through. So, a 2:1 ratio means for every 2 decibels of volume above the threshold, the compressor will only let 1 decibel of volume pass, thus reducing the volume.
The attack is how fast the compressor will trigger once the threshold is exceeded, lower values make it almost instant where longer values can let the initial transients of sounds pass through unaffected (a technique we will talk about later to make punchier drums). The release, then, is how long after the volume has gone below the threshold that the compressor stops working. Too fast of a release can cause an unnatural pumping sort of sound, while too slow can cause the compressor to continue reducing the gain after the loud parts are done, actually making the quieter sounds that follow even quieter.
Compressing for punchiness
So we've just talked about the basic function of a compressor, it's various controls and how to use it to tame the dynamics of the track. Besides this, there are actually other ways to use this tool on your tracks, and one of them is to make things really punchy. Most compressors max attack time is 30 milliseconds, which is the approximate time that a transient of an instrument like drums will be audible. By setting the attack time to 30 ms, you're letting the initial transient (the click at the beginning of the waveform) pass through uncompressed, while compressing the rest of the sound. When you then lower the threshold, you are increasing the dynamic range between the body of the drum and the transient, which will cause it to sound more punchy.
It is easy to overdo this, and having too much transient is definitely a thing. Remember that a lot of sampled drums you'll find have already been shaped to have a lot of punchiness, so you won't need to be throwing a compressor and boosting the heck out of the transients on every drum sound. It's just a tool in your arsenal to use when needed. Don't forget to make sure that your release is set properly so that it won't bleed into the transient of your next drum hit!
Compressing for Saturation
Another use of compressors is to add color, or saturation, to a sound source. Some compressors, particularly ones that are modeled after analog gear, change the sound as it goes through the compressor, it adds more harmonics giving the sound a certain character. It is usually a pretty subtle thing, but this is what people talk about when comparing different compressors. There are different use cases for various types of color as well as compressors that are completely transparent, because sometimes you don't want to alter a signal at all. A great compressor for transparency is likely the stock one in your DAW. I know the Ableton stock one works great for this. I'll link a few options below for more colored compression. https://www.plugin-alliance.com/en/products/acme_opticom_xla-3.html
Normally, a compressor reacts to the signal of the track that the compressor is placed on, and also affects that same track. However, there is a way to make the compressor actually react to other tracks in your project, reducing the volume of one track in relation to another. This is called sidechain compression. Many compressors, including most likely the stock compressor of your DAW, have the option to turn on sidechain. When you do this, you select another track as the source and the compressor will now be reacting to that track instead of the track it is affecting. There are many uses for this, and the basic idea is that in a mix you may want to dynamically push back one sound whenever another sound is playing so that they don't clash. One example is in electronic music we often will sidechain the bass to the kick drum. This is done so that we don't have a muddy low end and whenever the kick hits, the bass will duck out. I personally usually prefer to achieve this result by manually automating gain, but using a compressor's sidechain is another way many people will do this. Other uses include ducking instruments when the vocal comes in, ducking the percussion group when the kick and the snare hits, and much much more.
So we've talked about a few different ways to utilize one of the most popular and useful tools in a music producer's arsenal, the compressor. You can use it to tame your dynamics, you can add punchiness, you can use it to add saturation, or you can use it to sidechain from one track to another! What are your favorite compressor plug ins? Comment below! As always, I encourage you to hear how I use these principles to make music by listening to my music at Ryahu for dance music and philip j loaf-eye for Lo-Fi music.
Until Next Time!