Compression For Mixing - What The Pro's Don't Tell You

The internet is already replete with so many resources on compressors and what they do. So pardon me if I skip to the chase and talk about the compressor from an application point of view.

This post aims at helping you know what to expect sonically when you turn those dials on your compressor plugins and how to apply this musically to a mix.

Important note! 

For teaching purposes, we are going to assume a fixed gain reduction ratio of 3:1 and the threshold set to a level where the compressor begins to work.

For more information on compressor parameters - threshold, ratio, attack and release please visit link

Uses of compressors in a mix

There are two basic uses of compressors in a mix:

1. Dynamics Control.

2. Depth placement.

1. Dynamics Control

As history tells us, this is the trigger that inspired what we know today as a Compressor. Man wanted a way of averaging the loud and more quiet portions of a conversation, so they created a device that automatically reduces the levels of loud portions thereby making the quieter regions more audible - in a nutshell.

So how can this help in a mix?

Attack: A relatively fast attack of (0 to 30 milliseconds) will catch loud transients, make the vocals or instruments less 'in your face' and more inside the mix. Use a faster attack when you're okay with the levels of the track but still feel they're 'too present', 'too obvious' or 'too busy'.

Slower attack (30 milliseconds and above) means the initial transient of the sound might pass through seemingly unaltered. Use this to allow expression and the need for some instruments to breathe.

Release: A Faster release (about 0 to 60 ms) helps preserve some of the original dynamics/punch of the track. Use this to add presence or punch to a track.

A slower release (60 ms and above) reduces the presence/dynamics of the track and makes it blend more into the mix. Use this to make tracks present but not so obvious.

2. Depth Placement

Pan and reverb seem to be the reigning champions for spatial placement in audio production. But if pan covers the left to right axis and reverb makes up for the 3-dimensional room space, how do we simulate front to back distance (depth) during mixing?

Volume? Yes, but on its own volume might not always do a convincing job and that's where a compressor comes in.

Using the right SETTINGS and LEVELS, you can control the front to back placement of sound using a compressor.

Here's how:

To bring to front & with depth: Slow attack, fast release and adequate gain. Useful for pianos, kick drums, lead vocals etc. 

To send to back: fast attack, slow release and adequate gain. Useful for add libb vocals, back up vocals, trumpets, pads etc.

To bring to front & with reduced depth: Slow to medium attack, slow release and adequate gain. Useful for separating lead vocals from the mix, acoustic guitars, distorted guitars etc.

Punch through: fast attack, fast release and adequate gain. Useful for punchy kicks, bass, snare and even lead vocals.

A good mix is a lot like a good picture - some objects are big and in front, some are small and behind, some objects bold, some  dull, some to the left, some right. If all were big, bold and and in front the picture would look awkward. Same goes for music.

Written by,

Chidi Nnadi.