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What is mastering?

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Studio Mastering

There are lots of myths about the mastering process. What is mastering? Do we need it? If you've asked yourself these questions too, then seek no further - we'll try to explain what mastering is all about:

Origins and History

In the early days of electronic recording studios, bands still had to play everything live and in real time, using a single microphone and an amp. Recordings were cut directly onto acetate. Then the introduction of analogue magnetic tape technology created a new profession - the 'mastering engineer', whose job was to monitor the frequencies and levels of a recording, thereby keeping any needle jumps in check. Tape recordings were then transferred onto a template which would function as a master copy, enabling the large-scale production of vinyl records. Records are always limited in terms of their length of play, frequencies and dynamics. This still has to be taken into consideration when transferring master tapes onto vinyl. The role of a mastering engineer has constantly changed alongside the ongoing technological developments occurring in recording studios. When multi track recordings were replaced by 2 track master tapes, tools which we now call equalizers and limiters were introduced. These enabled the sound of the record to be improved upon before the final cut, a technique which was used increasingly during the pop music boom of the 50s and 60s. It was in this era that the role of the mastering engineer as we know it today was really established. The best mastering engineers have actually helped many records to achieve great success, just because of their talent in the studio, and they're well paid because of this potentially very significant role. Up until the 80s, demand for talented mastering engineers grew constantly.

Why is mastering used?

The main reason for mastering is: recordings should sound as balanced and as good as possible on any sound system - whether on a hi fi system, through headphones, on the radio, at a club or on a portable device. This isn't as simple as it sounds, as there are so many playing options, and so many different devices. The artistry of the mastering engineer lies in their ability to create a balanced sound whilst doing justice to as many different demands as possible. The main things they have to consider are: well balanced frequencies, a good stereo image, mono compatibility, and dynamics. There are many hardware and software options available to modern mastering engineers to help them achieve these goals. Equalisers are used to optimise frequencies, and compressors and limiters are used for dynamics. When mastering an album, the volume of each track has to be considered in the context of the whole record, as the listener shouldn't have to adjust the volume between tracks.

As vinyl records are produced relatively rarely these days, mastering engineers work primarily with data which can either be sent to CD pressing companies as a DDP file (Disc Description Protocol), or to the client (artists, labels, distributors) as a form of data (like Wave). The highly compressed audio formats which are used by digital shops such as iTunes sometimes require specialised mastering, which is often done according to the demands of the codec (e.g "Mastered for iTunes").

Digital vs. Analogue

Digital techonology has prompted a fair few debates since it became popular in the 70s. The commercialisation of the compact disc (CD) in the 80s, and the digitisation of recording studios are both examples of the sort of issues that have arisen. Analogue fans used to criticise the lack of "warmth" and the low resolution of digital recordings, which was originally due to their relatively low bitrates (16Bit). The storm has died down a bit since then, and most studios now use a healthy mixture of tried and tested analogue equipment combined with the latest digital technology (which has been extremely well developed over the last few years). The best mastering studios possess an impressive arsenal of top quality analogue equipment and Plug-Ins. Getting the monitoring right is also very important: it is essential to use neutral and balanced speakers! Mastering studios often have several different loudspeaker systems at their disposal, in order to make good comparisons.

One of the main mastering debates is over the increasingly limited dynamics in songs. Since the introduction of digital technology, recordings have been getting louder and louder ("subjective volume judgement"), due to increased use of compression and limiting. However, the song's dynamics often suffer in this process, as the natural changes between louder and softer passages are minimised. You can hear this effect most clearly on the radio, where dynamic processors and psychoacoustic effects are also used. The reason for this practice is simple: human hearing has always been programmed to think that louder noises are more important: that is why louder recordings sound subjectively 'better'. This situation has led to the much cited "Loudness War", which many currently famous mastering engineers are criticising, and rightly so. They want a revival of dynamics in recordings. However, dynamics depend a lot upon the genre of the song, and can be extremely varied. Perhaps young people's tastes have simply changed, and they just don't hear the bemoaned loss of dynamic difference.

Plug-Ins and Co.

These days you can get hold of some top quality software plug-ins! Many software producers undertake extensive research to try and emulate the sound of analogue equipment, and they often come very close to the original - for a much lower price. This is why the number of mastering studios has grown considerably, leading to a large decline in prices. Online mastering services have started successfully establishing themselves over the last few years too. Even famous mastering studios like Abbey Road offer discounted online mastering services these days, a method used by many studios to replace any vacancies with online requests.

The way things are going, artists will probably start to think that they can master their own records if they have all the right plug-ins. However, this would not really work for many people, due to two limitations common to normal/small home recording studios: firstly, they don't have a space with a specific and optimal acoustic, and secondly they lack the necessary listening equipment, or outboard equipment.


The most important thing for a mastering engineer will always be their sense of hearing. Years of experience and training are also essential.

The phrase "Fix it in the mix!" also applies to mastering - if a song is almost perfectly mixed, then it takes the pressure off the mastering process to sort everything out.

Many mastering studios also offer "stem mastering" - meaning that several tracks (usually 8 stereo tracks, divided into vocals, drums, bass, etc) are mastered separately, instead of a single mix being used. This gives the mastering engineer a stronger influence on the final product, and enables them to iron out mistakes individually.

Interested in delving deeper into the art of mastering? Be sure to explore our articles about electronic music mastering as well as how to finish a track properly and don't forget to try out our AI mastering tool for free!

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Get tips on How to Succeed as an Artist, receive Music Distribution Discounts, and get the latest iMusician news sent straight to your inbox! Everything you need to grow your music career.