Mastering the Mix

Over the next two weeks I will be mastering the remaining tracks recorded 12 weeks ago now for ‘Zed Leppelin‘. So lets look at the what and why of mastering and discover some of the important elements used to get a track or group of tracks to a place where they just as envisioned.

What is Mastering?

Mastering is essentially the conduit or intermediary between a great mix and a track or set of tracks that are fully ready for distribution. Mastering is all about polishing the original mix so that the end listener has the best experience possible.

Why the need to Master?

In Bobby Owsinski’s book ‘The mastering Engineer’s Handbook’ (2015, p.4), he outlines the main reasons:

  • “If you have a song that sounds pretty good by itself but plays at a lower volume when played after another song
  • If you have a song that sounds pretty good by itself but sounds too bright or dull next to another song
  • If you have a song that sounds pretty good by itself bottom heavy or bottom light against another song”

There are other reasons, such as if the mix was done in a mixing studio environment using bright and good quality monitors but when played on a home stereo or in the car sounds dull and lifeless, The mastering engineer is usually a highly skilled critical listener and can listen to the original mix in a studio specifically designed to discover where the mix may be lacking and bring it to life so that it sounds great in almost any setting. A mastering studio usually has several sets of monitors all with different frequency responses and character which aids this process.

The mastering engineer will usually use a process called A/B’ing which is a process of comparing the tracks he is working with to others of that genre that sound awesome and have been popularly received by listeners. There is no substitute for getting a guide from a popular or famous track which has the sound being sought and trying to align the one being worked on with it.

In addition, the mastering engineer focuses on bringing a smooth, consistent transition between songs on an album. When we are mixing, we tend to be directly focused on one song specifically at any given time. The mastering engineer seeks continuity between all tracks ensuring a smooth listening experience.

How does Mastering improve the sound of a Mix?

There are several areas that a mastering engineer will address to improve the sound of a song or a series of songs on an album. The primary ones are:

Equalisation: Perhaps the most important tool to the mastering engineer, equalisation (or adjusting the frequency content of a track), can greatly improve its listen-ability.

izotope 7
iZotope 7 Mastering Plugin was our choice when mastering our film project

Some tracks may have too much bottom end or be too tinny at a higher frequency and it is the skill to hear these problems and apply corrective EQ to the areas needing help that is one of the key skills in this profession. Sometimes, the engineer doing the mix may have done too much EQ themselves when they did their mix (same with compression), and it is quite common for the mastering engineer to send the mix back and ask for this to be backed right off so he can do his job to the highest standard. The mastering engineer will generally only boost or reduce different frequencies in small dB increments, whereas when mixing, we tend to use boost or reduce at much higher dB levels.

Compression, Limiting and Balancing levels: The compressor and limiter are two key tools a mastering engineer will use to really bring power and punch to the finished tracks and once again, a mistake made by many mixing engineers is to compress too heavily before the mastering stage which reduces the mastering engineers scope to do what he does best.

iZotope 7 Compressor showing the key settings

The mastering process generally only ever applies gentle compression as if too much compression is applied one can actually hear the compressor kicking in which can make the overall audio sound a little fabricated. The mastering engineer will most often use what is called a multi-band compressor. This type of compressor is very useful as it divides the frequency band of the audio into different sections which can be controlled independently, meaning that different compression levels can be applied to the different frequency ranges without affecting what is happening to other bands.

The limiter is a little different to the compressor in that it squashes or regulates the large peaks in the audio bringing them back into line with the rest of the track. The compressor takes care of the medium and lower level signals. A limiter will ensure that these large peaks in amplitude will not allow digital clipping. It is usually as a result set to a very fast attack time so that it reacts quickly to these peaks and creates a ceiling which they cannot pass through.

The relative levels between each track having continuity in an album is a key role for the mastering engineer for obvious reasons. One track cannot be calm and quiet and be followed by a much louder track. Compression helps here also.

Noise Removal: There may be electronic clicks or pops in the mix that has been provided to the engineer and he will use complex software like RX to remove these at the mastering phase of production. This software can also rid the recordings of plosives (P’s and B’s), and excess siblance (S’s).


The mastering stage is also a time to look at enhancing the stereo width of the audio and ensure that the fades in and out of each song are sounding natural. How the audio is mastered is dependent on which platform it is being delivered to and loudness standards (read my blog on this topic here), need to be checked via metering to comply with the delivery format. The consequence of not ensuring these levels are correct may mean that the overall sound of the songs will be affected when they arrive and are exposed to the particular delivery formats algorithms meaning that all the work that has been done can be in vain…


Owsinski, Bobby The Mastering Engineer’s Handbook (3rd Edition), 2015


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