Mid Side Compression:
Controlling Your Space

Mid Side Compression offers an incredible way to subtly enhance the space or air in the image of a mix.

And, as a remixing tool, it offers an alternative when static methods (such as mid side EQ) can leave you hopeless.

It involves controlling the dynamics of the mid (mono) and side (pure stereo) elements of a mix separately from each other.

One of the most popular uses of mid side compression is to tame a vocal that's too dynamic or poke-y.

It's still important to understand that at the mastering stage you're only working with frequencies now, and the procedures described can have the effect of taming a vocal if used correctly.

Instead of applying compression to the entire signal it's applied to the just the mid channel where, 99 per cent of the time, the vocals will be.

Of course, you have to be sure that you're not going to create out of phase artifacts.

So, no more than 2 dB of reduction should do the trick.

However, I like to use this technique sometimes to lightly enhance the stereo field of a mix. Not to tame vocals, but just to apply a very, very gentle compression action of no more than 0.5 dB gain reduction. This adds a nice sense of air when needed.

On another note...

There are times when the vocal seems to be occasionally buried in the mix. In this case, you apply compression only to the side channel.

The UAD Fairchild is perfectly suited to do this type of work, with just the flip of a switch, without needing to set up as described here. Although this software is modelling analog gear, I've not heard any de-correlation issues.

There are variations to this approach:

In the case of the buried vocal, we can increase its presence by adding density to the mid channel instead.

Here, you apply a gentle, transparent compression to the mid element at, say, no more than 2 dB – and recover that reduction with the make up gain!

Be aware that not only will you be 'bringing up the vocal', but also all the centred instruments in the mix: the kick, bass, maybe the snare as well as other rhythm elements of the mix.

Are you beginning to see some creative possibilities, here?

By compressing just the side element in a similar fashion, you can enhance the space and width of your stereo mix without introducing phase issues.

And by using a multiband compressor, you recover more control for fixing the aforementioned vocal issues.

De-essing can be made more effective by compressing only the sibilance frequencies in just the mid channel.

I once needed to basically remix a client's project to, among other issues, bring up the vocals.

I used this set-up, and UAD's Multiband Compressor on both the mid and side channels, carefully setting the appropriate crossover points identically on each. Additionally, using some light upward expansion on the upper side channels as well as mild compression on the lower sides, the project was a success!

I urge caution as this technique should not be used haphazardly – it really is a method of last resort.

Improperly used, you could end up having your stereo image noticeably widen and narrow.

So, the final point and most important thing to always remember, especially with mid side compression, is to - Big Surprise! - listen.

Carefully!

Return from Mid Side Compression to
Mid Side Mastering

Return to About Audio Mastering Software