Pro Audio Files

What is Mid-Side Compression?

Hey, guys. Matthew Weiss here —,, and

I want to talk about Mid-Side Compression. Now, mid-side is something that tends to throw people for a loop a little bit, but it’s actually pretty simple.

Basically, when you have a stereo playback system, instead of thinking of things as left and right, what we do is we think of things as middle and sides. So anything that’s playing out of the speakers at exactly the same level and exactly the same time, that’s going to be heard as the phantom center. That’s going to be our mono middle.

Then everything that’s different — everything that’s playing either at different times, or it’s different material on the left versus the right, that’s our side information. So mid/side is just a way of identifying that different information and effecting it.

It’s really no different than affecting say the left versus the right.

So what’s an example where we would maybe want to manipulate the middle and sides differently? Well let’s say we have an overhead capture like this one.


Now this is a pretty tight capture. This is good for say, something like a Funk kind of thing going on. It’s pretty centered, it’s tight, it’s focused mostly on the snare, but let’s say that we wanted a bigger, rockier kind of sound. We want to bring out those overheads and we wanted a roomier capture in the overheads.

Well, maybe we would want to do some kind of mid/side situation so that we can bring out all of that side information. Like so…

[overheads, mid/side adjusted]

One more time, before and after.

[overheads, before and after mid/side adjustments]

It’s pretty cool right? The snare itself is kind of staying in the same place, but the room around the snare is coming up and all of the cymbals are coming up. So I’m going to show you how to construct that using the FabFilter Pro-C2.

Obviously, we have to pull up the Pro-C. There we go. And I’m going to set it to a hard knee. I’m going to use this clean style, take off the auto-gain here, and I’m going to turn the look ahead on. So now I’m going to start playing around with these controls.

[overheads, adjusting Pro-C2]

So here we’ve set the compressor so that it’s really reacting very heavily to the snare but the problem is everything is getting pulled down with the snare, right?

[overheads with Pro-C2]

We’re getting some pretty heavy pumping going, so let’s say that we want to affect the middle of the snare without affecting all of the sides. What I’m going to do is I’m going to go to the Stereo-Link and I’m going to turn it all the way to where it says “mid-only.”

[overheads, Pro-C2 in mid-only mode]

Now we’re just affecting the middle signal.

[overheads, with and without Pro-C2]

Alright, pretty cool. So then of course, obviously we can just use a little bit of make-up gain, and effectively what we’re doing is keeping the snare at the same level, but we’re bringing up all of the side information.

[overheads, with Pro-C2]

Now of course, we can also do the opposite. The FabFilter company really sort of centers it’s brand around being very, very versatile. Anything that you can imagine, you can do. So one of the cool things that they’ve got going here is you can do this not only just for the mid, but you can do it for the side signal only. Because right now, this is just the mid signal feeding the detector of the compressor, and acting on the mid signal.

But you can do the same thing on the side, so that you would have maybe like, the hats and the cymbals triggering the compressor. But you can also do it with the mid signal triggering the compressor, but the compressor acting on the sides.

I’m going to switch into that mode, and what you’re going to hear is pretty much the exact opposite. Now, every time the snare hits, the sound is going to really tighten up to the center.

So before…

[overheads before Pro-C2]


[overheads, after Pro-C2]

You would use these in totally different applications. If this was a drum kit for maybe a hip hop band, and I wanted to have that really, really punchy, almost sample like sounding center snare image, I might be interested in doing this mid triggering the side effect.

If I’m doing a rockier sound, where I really want the overheads to bring up the room, and I want the cymbals to be really bombastic, then I might just want the mid acting on the mid. So you know, there’s a lot of different situations where you might use different versions of this mid/side processing, but the bottom line is that using these very versatile plug-ins like what FabFilter makes, you pretty much do whatever you imagine or intend to do. Which I think is pretty cool.

So I hope that explains some of the use of mid/side processing and mid/side compression. But yeah, until next time guys.

Matthew Weiss

Matthew Weiss

Matthew Weiss is a Grammy nominated and Spellemann Award winning audio engineer from Philadelphia. Matthew has mixed songs for Snoop, Sonny Digital, Gorilla Zoe, Uri Caine, Dizzee Rascal, Arrested Development, 9th Wonder, !llmind & more. Get in touch:
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