Compression (Sound On Sound)

Compressors Part-1
Compressors are useful tools, but just like anything, they can be over-used and even abused.  Here are some tips on the use of compressors.
Compressors on every track Do Not Mix Your Song!
I have seen projects come from what I thought were reputable studios and engineers, but every single track had a compressor inserted (LA-2A). The threshold on each one was set so that the gain reduction meter hovered around -20dB. I called the engineer and asked why. He said, “I use them to automatically mix my tracks. The compressor takes care of all the level riding just like I was using the faders.” I sat with my mouth hanging open for what seemed like an eternity.
At first glance it seems like it would be a good idea, but what about the sound? A compressor does not just change the level like when you ride a fader, it COMPRESSES the signal. As the signal gets louder it is squashed by a percentage of its value. I would compare this technique with a hamburger grinder. Put in beef, you get out ground beef. Put in ham, you get ground ham. It is easy to tell what meat you put in, but it is very hard to tell what meat comes out.
It is possible to set up a compressor to average the volume level of a signal, but it can’t make fast changes without changing the sound radically.
Compressors are for changing the sound by changing the dynamics of the sound. It makes the soft parts seem louder by compressing, or squashing the loud parts. Sometimes this is desirable to make a vocal float on top of the track instead of getting swallowed up in the track. The same is true of most solo instruments. If the solo is compressed a little it sounds like the player has moved to the front of the stage.
For those new to compressors, some basic knowledge of compressor settings will assist in the following explanation. The five most common settings are:
Input Level or Threshold: This setting tells the compressor at what level it should start working. Any signal below this level is unaffected. Compressors with an Input control have a fixed threshold. You turn up the Input Level until the audio goes above the threshold. Compressors with a fixed Input Level have a Threshold adjustment. You turn the Threshold lower until it is below the level of the audio.
Ratio: Is how much the sound is being compressed. A ratio of 1:1 means the compressor is doing nothing. The output is exactly the same as the input. 3:1 means that for every 3dB of input level rise, there is only 1dB of output level rise. Some compressors allow negative ratios. This means that the compressor is acting as an expander and makes the output louder than the input.
Attack: Is how fast the compressor starts to act on the incoming audio. A slow Attack allows some of the audio to come through before the compressor starts to compress. A fast attack does not allow transients to get through unaffected.
Release: Is how long the compressor waits after the audio has dropped below the threshold before it returns the gain to the value before the audio exceeded the Threshold.
Output Level or Makeup Gain: Remember, the compressor lowers the level of the audio by turning it down. You must turn the level up to get the volume back to where it was without the compressor. Some compressors have an automatic setting for output level or a switch called “Auto Makeup.”.
There are some Rules-of-Thumb that I follow whenever I add compression to a track.
Set Ratio at 2:1
For now leave Attack and Release at the preset levels that were present when you loaded the compressor.
While watching the gain reduction meter, change the threshold (lower) or input level (higher) until the gain reduction reads about 3dB with peaks going no more than 4dB.
Finally adjust the output Level or Makeup Gain to get the level of the audio back up to where it was before compression. If the compressor gain is automatic, then leave it alone.
Now listen. It sounds pretty good. Ninety percent of the time, this is as much as you will have to do when compressing an instrument or vocal.
Don’t do any tweaking to the compressor settings yet. Get further along with the mix, compress other tracks that you think may need it, and then take an overall look at the mix listening to all of the tracks in context. At this point you can go back to a vocal, for instance, and change the ratio a little, or change the threshold a little, and see if these new adjustments make the song sound better or worse.
Remember that it is usually easier to tell when something is wrong than it is to tell if something is good. When you make adjustments that do not improve the sound, put the settings back, then try another adjustment. Go through the permutations, “That’s not better. No, that’s not better. None of the changes are better.” If that is the case, then it is as good as it can be, which is all you are asking for