Mix bus compression. Do you do it? Should you do it? First off, let me explain what I’m talking about.
When you’re mixing a song, regardless of what DAW you’re using, all of your audio tracks are being fed into a single mix bus. This is normally represented by a master fader of some sort.
When you’re first starting out mixing, the main goal is to mix everything at a decent level without clipping your master bus. As long as you’re happy with your mixes, you can keep doing this…and you don’t have to read the rest of this article.
However, a lot of mix engineers use some sort of compression on the master bus. They’ll slap a compressor or limiter on the master fader. There are several reasons to do this…and not all of them are necessarily “good” reasons.
Let’s take a quick look at a few examples of why you might want to use compression on your entire mix.
Scenario #1 – You’re client wants a demo CD to play in the car.
This is a common request. You finish up a recording session, and before the artist goes home, she would like to take something with her to listen to between now and the next session. (If you’re an artist, you know what I’m talking about. You just want something to listen to, right?)
In this situation, you could simply do a bounce of the song, burn it to CD and send her on her merry way. However, chances are your phone will ring thirty minutes later, and she’ll say, “Something’s wrong with this recording. It’s too quiet! It doesn’t sound as loud as my other CDs.”
What your client may not know is that the audio on a finished, mastered CD has gone through a LOT of compression. Her music will need to be both mixed and mastered before it will be at a relatively “normal” volume.
You can try to explain this to her, and explain why it’s not a faulty recording, but there’s the chance she may start to doubt you a little.
I know, I know. This is probably an extreme example, but it can certainly happen. For this reason, a lot of engineers will simply throw a compressor and/or limiter on the master bus right before bouncing the song down for the client. Since the client knows it’s a rough mix, she won’t expect it to sound perfect, but at least it will be plenty loud.
Scenario #2 – You want your mixes to sound like they’ve been mastered.
In the first scenario, we applied compression/limiting to the mix for the sake of the client, NOT the mix.
However, as you’re working on a project, and listening to your various mixes, you may get the urge to squash them with some compression and limiting to make them sound more like a “polished,” finished, mastered recording.
Here’s where things can get dangerous. Now you’re changing the sound of the mix. Mixing and mastering were meant to be two completely independent phases. When you start trying to mix AND master at the same time, you’ll inevitably do a poor job of both.
What ends up happening is you use too much compression, and you begin to rely on the compressor and limiter to achieve that “sound” you’re going for. This is a backwards work flow.
You should use the normal methods of mixing — EQ and compression on individual tracks, effects, automation, etc. — to make your mixes sound good. As soon as you start relying on the mix bus compression to save you, you’re going down the wrong path.
This isn’t to say you shouldn’t use ANY compression during mixing, but you need to be clear as to why you’re using it. Keep mixing and mastering separate.