What is Audio Mastering?

The Definition of Audio Mastering

So what is audio mastering? What does it mean? The term audio mastering as we know it today derived from an older term known as 'premastering' which is the process of preparing a finished mix to be pressed to vinyl disk. The preparation will typically involve EQ and compression aimed at balancing tone and controlling levels, equipping the track with ideal sonic characteristics for pressing to vinyl. The term 'premaster' referred to the recording immediately prior to having the 'master disk' cut from the cutting lathe. Therefore the term premaster would assume all mastering processes like EQ, compression and limiting had been applied. Nowadays the term premaster is more commonly used for a finished mix before mastering processes have been applied. A mix engineer may bounce down a finished mix to a stereo file and then refer to it as the 'premaster' as it is about to be sent off to the audio mastering house for further processing.

So what is the purpose of premastering; why does further processing have to applied to a mix before it can be pressed to vinyl?

Playing a record has its physical complications. The kind of processing required is determined partly by the limitations of the consumer's player, but also by the limitations of the vinyl disk itself. For example, if there is too much happening in the extreme low frequencies, the needle can literally rattle itself out of the groove of the disk. Too much stereo information can also cause the same thing to happen.

Fortunately you don't have to worry about this. The Audio Mastering Blueprint is aimed at preparing and enhancing a mix for digital reproduction like CD duplication, or internet download where there are fewer limitations.

Premastering is a purely technical process spanning back many years. An enormous amount of skill is required to obtain the most out of the dynamic and tonal limitations of a vinyl disk. Preparing the mix is only part of the battle, there's also the operation of the cutting lathe used to create the master disk. Nowadays, down to the current way we consume music, and thanks to advances in plugin technology, the premastering - or 'mastering' process - has become accessible to the individual artist/producer. In fact, mastering has become very much an art in itself, playing a major role in the musical attributes to making a record. Let me explain a little why the mastering process is still so important, despite not having to worry anymore about the physical complications of pressing to vinyl.

As mentioned, the limitations of the vinyl disk were only a small part of the reason that mastering processes like EQ and compression would need to be applied. The other reason – which is the reason that concerns you – is the limitations of the consumers player, and the environment the music is being played in.

Think about when you're recording your own music, producing for a band or mixing for a friend. The likelihood is that your listening environment is free of noise and distraction, and your speakers are of at least fairly good quality. The problem is that when the recording reaches its audience, the music player and listening environment are likely to be very different compared to that of when it was produced, which can dramatically change how the mix sounds. Did you know that your environment may be leaving an impression in your mix? And so might your good quality speakers. The trouble is that you would never notice this fact until you play your mixes on another, perhaps inferior system somewhere else. When I was a kid, I used to take my own recordings to my friend's house and play them on his middle of the road hi-fi, but they never sounded as good as they did at home. They were un-clear and sounded small, yet when playing a commercial CD, everything sounded big and crystal clear, at much lower volumes. This is because the music on the commercial CD had undergone professional mastering making it sound its very best on that particular hi-fi and all other music players too.


Even fairly expensive speakers are not always one hundred percent true. By 'true' I mean reproduce every frequency at the same level. If your speakers are a little bass heavy, you will naturally compensate in your mixing, and vice versa. It goes without saying that the flatter your speaker's frequency response, the more suitable they are for mixing or mastering. In most cases, a 'studio monitor' will be designed to have a relatively flat frequency response. However, what's of more concern is how your room itself can alter the tone of what you are hearing, especially in the low frequencies. One of the targets of the mastering engineer is to correct the tonal imbalances derived from an imperfect listening environment. For this reason, it is of extreme importance that your listening environment be as neutral as you can get it. The next chapter contains a guide on how to do just that. Your listening environment is a crucial factor in creating a well balanced master.


Why did I need to turn my mixes up so loud in order to hear all the details?

My listening environment at home where I produced the music was free from any noise or distraction – I could hear the detail just fine there. At my friends, there might have been people talking, moving around, playing computer games and who knows what. The subtle quieter details would be lost unless I cranked it up. Mastering combats this problem. By the use of dynamics processors like compressors and limiters, mastering is able to surface every little detail – the quiet bits become louder but don't sound like they have been turned up. Achieving this to the greatest effect is very much an art of mastering. Apart from background noise, you're also up against the quality of the speakers the music is being played on. My friend's hi-fi wasn't bad, you could hear the kick drum and bass line at least. But what if I played my recordings on some laptop speakers? They wouldn't have stood a chance.

Mastering equips a finished mix with the power to sound correct on whatever system it is played on. It does this by manipulating the dynamic and tonal content. At this point I won't go into detail on how this is done, all will be explained as you proceed through the mastering tutorials. I will just say now that by the clever use of compression and EQ, an entire mix can be distinguished on a speaker that only reproduces around 75% of the frequencies inherent in the mix.

Just mentioned are the more practical reasons for audio mastering. There are many more exciting reasons within this mastering tutorial which are of a more musical nature – things like fattening, adding sparkle, creating loudness, tightening a loose bass-line or adding extra depth and space. As you practice the techniques, you will realise the immense power you have in creating a more exciting musical experience.

Before we start looking at the techniques and methods, it's important to ensure our listening environment is as neutral as possible. The next chapter will explore this further...  Studio Acoustics- A Guide to a Improving the Acoustics of Your Listening Environment.