Compression: what and why?

"Compression", in essence, does nothing more than any other audio component does.  Compression controls the input signal of a sound and therefore, sets a new output.  Sometimes it's needed!

Compression also serves a basic purpose.  Basically, its purpose is to "breathe" with the track and make the sound "punchier".  It plays with the dynamics, but NOT with the sound.  The changes it makes to the dynamics of sound should be subtle ( +-3db but no more in actual tweaking).  There is a second part to compression that we will discuss at a later post that will take care of altering the sound itself.  For now, think of it as:  subtle changes in dynamics. 

You know when to use compression if you need to add color and brightness as well as fullness to a track.  To make the track sound more real. To make the sound "flow" better and "blend" better with the rest of the tracks. 

Should you use it before or after EQ?  My experience has been NOT to use it after EQ'ing.

Put prior to EQ because if not, the compressor will compress what's getting emphasized by the EQ.  Maybe, you have worked so hard at EQ'ing something that needed compression anyway.  And besides,  since compression is about dynamics, is a bit more fundamental.  EQ'ing is almost more artistic/stylistic. 

The following items are common in compression and it's beneficial to be familiar with what they do:

1. Ratio - for ex: for 4 db "in" to 1 db "out means that 25% of the input will be emphasized. 

2. Threshold - compression will occur above the threshold db and not below. 

3. Attack and Release - best at closest to midway point.  This is actually the "attack" and "release" of the sound.  So work on attack at longest and release at shortest. It's a good place to start!

4. Gain make up - make up the gain that's lost in compression.  Compression = Lost Gain therefore it may need to be made up for. 

5. Bypass - lets you hear how much gain is lost to help you decide how much to turn the Gain make up on.   

Procedures to set up of compression:
1. Click bypass to hear no compression first. 
2. Un-click bypass. 
3. Then Attack to its longest and Release to its shortest and work from there.
4. The rest of the controls will become clearer once you have figured your attack/release settings usually. 

Compression with vocals:
Usually on a pop song, the vocals have to be on top of the band.  Compression makes it seem more real. Words do not drop out and the voice is emphazised. Usually needed in pop.  For a stronger instrumental sound, attenuate the vocals to be more at the level of the band.   

Brief summary:
Compression affects Dynamics and it needs to be solid.  It keeps the dynamics real and without drastic changes in it by bringing down (compressing) the peaks and up (compressing as well :) ) the sounds getting lost.  Hence the word:  COMPRESSION.