What Is Compression in Audio?

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In this video, I wanted to talk about compression. Compression is one of those things that a lot of people struggle with. And it’s one of those tools, those fundamental mixing tools, that can harm your mix if used incorrectly. And I’ll cover some tips and things like that in another video, but I wanted to just introduce you to a compressor and really sort of clear things up on what the tools of a compressor are, you know, what the elements of it are, and how you can really use compression and what it does.

So one way to think about compression, and I think it’s a helpful analogy, is to think about where it came from. So back in the day when people were recording music and mixing, sometimes, people, for example, might sing louder at a specific point in the song. It might get more exciting to them. They might just project louder. So they would produce more volume.

And back in the day, you know, when that happens, you don’t necessarily want a track to have… a vocal track to have just two different volumes. You don’t want it to be, you know, some parts really quiet, some parts really loud. That can be not ideal. So back in the day, what they would do is you’d have someone who would just sit there and ride the faders, ride those volume faders. And so if a emotional part was coming up, they’d be like, “Oh, he’s about to belt this note out. I’m going to turn it down a little bit.”

But after a while, you know, we had this DAW revolution. We have this digital recording revolution. And we had a technological revolution. We created things called compressors. And that’s what compressors do. They basically do the same thing as that guy who was riding that fader to turn the volume down at the peaks to make sure that everything was balanced out. That is what compressors do.

They can just put a lid on what the volume is by literally pushing down and compressing the audio signal. So if I’m looking at this waveform here, you see that there are peaks and valleys, right? But then, if you look at here, you can see, whoa, these parts are way higher than the majority of the song.

So that’s where, back in the old days, someone might have turned my vocal down. They might have been like, “Oh, Scott’s really crushing this right here. Let’s turn that bad boy down.” Now, we can use compressors. And compressors can push that volume down. But, and this is a word of caution, if you’re using compressors, you have to be wary of over-compression.

You have to be wary of pushing too much down on that and killing what’s called transients. And all you need to know about transients is that they’re good and you want to preserve those. There are certain audio phenomenon and frequencies that exist, and transients are good.

So if you crush everything by over-compressing it, you can kill the life of a vocal, specifically. You can also kill, if we were compressing a piano, you might kill some of the natural sound of it. If we were compressing guitar, or whatever, you might kill some of those great natural sounds. And there’s a lot of debate around whether you should or should not compress vocals.

I tend to think compressing vocals should be a last resort. You should try to do everything else to not compress vocals. But using compression well is key here. So okay, we’re looking at this compressor here. Let’s talk about what our settings are and what exactly is going on here.

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