It is much easier to hear the reverb, EQ, or a delay effect and how those processing tools affect sounds. But hearing compression is definitely a challenge for beginner mixing engineers.
So, the goal of this post is to help you learn how to hear compression in 5 easy steps.
The funny thing is that once you start hearing compression you can no longer un-hear it, once you get it, that’s it.
One thing that helped me hear compression was a few exercises that were recommended by my teacher in music production school.
What I’m not going to cover in this post is the basic stuff about how to use a compressor or its parameters.
To get the most out of this tutorial, make sure that you already know or at least have an idea of what’s attack, release, threshold, ratio, and make-up gain.
Even if you don’t fully understand those parameters, the exercises I’m going to recommend will help you get a better understanding.
You should aim to learn each parameter one at a time, don’t try to grasp everything at the same time.
Let’s start with the basic things you’ll need.
Step 1 - The Session
The first step is to start a new session.
Load a snare loop in your session.
Add a compressor to the channel. For this demonstration, I’ll be using the FabFilter Pro-C 2 since it’s much easier to understand and has all the necessary parameters.
Next up you’ll need to set the knee from soft/medium to hard so that the compression will be aggressive and much easier to hear.
Set the ratio to 8:1, set the attack parameter to fast (0.005ms), set the release to 250ms, keep auto-gain switched on, and finally push the threshold till you get a gain reduction of -10dB.
By the way, you can do this exercise with any compressor of your choice.
If you’re also using the FabFilter Pro-C 2 to follow this exercise then your compressor settings should look like the one in the image below.
Step 2 - Hearing The Attack
Step 2 is all about learning to hear what the attack parameter does to a sound.
I want you to have 3 different settings on the compressor.
First, listen to the snare loop with the fastest attack settings (0.005ms). One thing you’ll notice is that the transients of the snare will be reduced and the snare will sound smoother.
Once you’re familiar with that smooth sound, stop the loop then switch to a medium attack setting (30ms).
For most recordings, the transient is usually 30ms long and anything after that is the decay or tail of the snare.
Listen to that attack setting for a while, keep bypassing the compressor to see if you can hear what the compressor is doing to the sound.
You should be able to hear most of the transient passing through unaffected and the snare now starting to sound punchy instead of sounding smooth. You’ll also notice that the gain reduction has decreased drastically without you touching the threshold parameter.
Finally, switch to a slow attack setting (80ms). Now you should be able to hear the most of the transients going through without being affected.
The snare should now be sounding much more punchy and there’ll be a very minimal amount of gain reduction happening (about -2db), again without touching the threshold parameter.
With some snare drums, if you go past 80ms on the attack there’ll be no compression at all.
Now, you just need to keep switching between fast, medium, and slow attacks till you’re familiar with the different settings.
They say "a picture is worth a thousand words" so I exported the different attack settings so that you can be able to see the differences. It’s much easier to understand what’s going on when you see the results.
Now that you know what the attack parameter does to a sound, it’s time to move to the release parameter.
Step 3 - Hearing The Release
To be able to hear what the release parameter does to a sound I recommend you to set the attack at 30ms so that you can get enough gain reduction without choking the snare.
Now, you need to do the same process that you did with the attack. Start with a super-fast release (this usually starts at 8-10ms on most compressors and doesn’t go below that).
This will give you a more aggressive, grittier sound. Keep bypassing the compressor till you can clearly tell what the compressor is doing to the snare drum.
Note that you’ll get a grittier sound because the snare is percussive, on a sustained sound you may get pumping and ugly distortion. But for now, let’s focus on the snare.
Next up, switch to a medium release setting (start with 300ms). Now you should start to hear the decay and room tone being brought up, this will also increase the perceived loudness of the snare.
If the snare was recorded live, you should start to hear the snare ringing and be able to tell that it’s a live recording (because of the ringing).
At this point, in most cases you should be able to hear that there’s no need to go any further with the release without messing up the sound.
But for learning purposes and to be able to hear compression then next you’ll need to switch to a slow-release setting (2500ms).
The snare should now be smoother and more controlled.
The compressor won’t be able to go to rest and will overlap with the next transient. Resulting in a quieter sound and may kill the life out of the snare if the snare hits are too close to each other.
The final step is to keep switching between fast, medium, and slow-release settings till you can hear the difference clearer.
Doing this in a section of a song that has a snare drum fill will speed up your learning curve.
Step 4 - How to Hear Compression on Sustained Sounds
Before you can jump onto learning other parameters, I would recommend you to switch from a percussive sound into a sustained sound.
Do this on a piano loop that plays sustained chords or a bass that plays long notes.
Apply the same process mentioned above, start with the attack then play around with the release. You’ll notice a big difference with the release settings when it comes to sustained sounds.
You’ll start to realize that, unlike percussive sounds, a fast release with a long release setting works better for sustained sounds.
Those differences are what will help you learn how to hear compression much faster and learn how a compressor affects different sounds.
Finally, learn how to hear compression, control dynamic range, shape your sounds, and add attitude/character to your sounds...
Step 5 - The Ratio
Once you understand attack and release then half of the job is done.
Then it will be a good time to jump into learning how to hear the ratio parameter on a compressor affects sounds.
The ratio determines how aggressive or transparent the compression should be.
To practice how to hear compression ratio on the snare, then simply set the attack at 15ms, release at 250ms, hard knee, and push the threshold till you get a gain reduction of -10dB.
You’ll notice that lower amounts of the ratio will give you a transparent compression sound while higher ratio settings will sound more aggressive and the compression will sound obvious.
Once you follow the steps mentioned above for 5-7 days straight you should easily learn how to hear compression and have a clear understanding of how a compressor affects dynamic range and shapes the envelope.
Then the next step will be to practice with other parameters such as the knee, hold, range, gain, etc. which will be much easier to grasp.
Don’t keep switching between different compressors, choose one compressor and stick to it till you master it and then all the other compressors will be easier to navigate.