If it is possible to improve expression in an individual part, is it also possible to improve expression in a gestalt?

Mastering is an Audio Engineering specialty that involves EQing and compressing FINISHED MIXES in order to prepare music for final output to distribution.  When music was distributed on vinyl records with severe volume limits, engineers had to find the best way to make the music sound good when being played back from the vinyl.  In other words, if the playback from vinyl will lose some treble, the mastering engineer may add treble to compensate.  Most songs benefit from mastering by being stronger, clearer, thicker, etc.

The most difficult part of mastering is deciding whether or not to sacrifice dynamics for compression and volume.  Is it better to have very dynamic music that gets quiet and loud or to have a song that is compressed to be as loudly as possible (or even louder than other artists’ songs)?

Although a mix should be the final sound of a song, it is often necessary to perform additional processing after the mix is completed, usually for one of three reasons:

1. Compensate for a misleading mixing environment. Even if an amplifier and speaker combination produces a flat and even frequency response curve, room acoustics, speaker placement, worn speakers, and even ear fatigue may cause certain frequencies to be overly emphasized or hard to hear.  Compensating for this inaccurate sound will result in a mix that may sound right in that particular room but horribly wrong in others.  For example, mixing in a room with overly bassy speakers will cause you think the mix has enough bass when in fact it does not. Frequently switching speaker types while mixing minimizes this need, but rarely negates it.

2. Improve the sound or enhance the song’s expression.  Mixing involves processing a group of sounds to enhance the expression of both each individual instrument and also the combined mix (gestalt) of those instruments.  It is often possible to further enhance the sound of a finished mix using compression (such as making a mix more solid by “beefing up” softer parts and making the mix more dense) and/or equalization (such as adding more high frequencies in order to more clearly hear the instruments in a muddy mix).  Remember that such processing is a creative process rather than a technical one

And yes, it is possible to apply certain mastering techniques while mixing.  Mixing engineers often will place compressors, equalizers or even other effects on the Stereo Mix faders of an analog, digital or virtual mixing console in order to be able to process the gestalt as well as individual instruments.  However, such use rarely negates Mastering.  I have heard of Mastering that was no more than choosing which type of tape machine or even wire to use, and others that were as complex as actual mixes (complete with volume changes at specific places in the songs).

3. Optimize the song for final output. Once a song is finished, what will happen to it?  If it is to be used in an album with other material, it needs to be sequenced (placed into a specific order) and may even need to be processed in order to better fit in with the other material (so the song does not stick out as being obviously different).  Songs may need to be a different volume or even may need to be given a different tone using EQ.

In addition, songs may need to be made louder in order to meet public demand.  Although once upon a time dynamics and soft song sections were appreciated, today consumers just want songs as loud as possible.  Record companies actually fear that if their song is not as loud as other songs they will not sell as many copies.  This is a silly thought, but it that has nevertheless caused music to have less dynamics as they are packed into dense blocks.  Heavy limiting (compression with a hard ceiling that cuts off dynamics) is often used for this purpose.

NORMALIZING is when an audio clip is analyzed for the loudest peak, and then the volume of that peak is set to 100% volume while the rest of the song brought up the same amount.

After songs have been processed in Mastering, they are placed in their specific order and the quiet times between the songs are adjusted (sometimes you want the next song to come in while you are still feeling the rhythm of the song before, sometimes you want enough of a space to allow the listener the chance to feel settled, etc).  Then a “MASTER” copy is made with all the usual information (Artist, Producer, Sales tracking codes, etc).

Mastering can improve the gestalt of a Mix as well as compensate for a bad (or even different) Mix. It is a creative process, similar to Mixing.