What is mastering? Why does it matter?

The purpose of mastering is to ensure that a track is completely balanced and optimised for a variety of playback formats and speaker systems. Putting it simply, mastering is the final polishing stage of audio or music production, which enables the song to compete with the same level of finish as other commercially released material across all platforms.

Chevy confused about mastering
Understanding Mastering

Making sure that your song sounds great to the listener across streaming platforms, the radio, and the dancefloor is extremely important. Many club systems and portable bluetooth speakers are mono so your track may sound different there, and for example, striking the balance between having your song sound bassy on a small speaker and not too overwhelming on a club or hifi system.

What the audio mastering process looks like in reality;

  • Repair and preparation
  • Equalisation (EQ)
  • Compression*
  • Saturation*
  • Limiting and Finalisation

Repair and Preparation

The first stage is to ensure that the track is healthy and there are no glaringly obvious errors, pops, clicks, or damaged audio in the files.

An array of tools are used to achieve this but typically audio is cleaned up with de-clickers, de-essers, and other similar audio repair tools. Plugins like Izotope’s RX7 suite are absolutely fantastic at cleaning up problem audio.

Furthermore, the engineer would reach out with any tips or quick fixes that might be best addressed in the mixing stage to ensure the very best sound.

Equilisation (EQ)

Secondly, Equilisation or EQ is applied across the master channel to balance out the mix.

This could involve fattening up some bass, removing some harsh frequencies or making a vocal pop a touch more.

There are hundreds if not thousands of EQs available in today’s market, each with a different flavour. These range across a scale of simple traditional tilt EQs like a Dangerous BAX, or more complex mastering EQs like the Manley Massive Passive.

Saturation is added naturally through careful selection of which type of EQ will work best for your track – no two equalisers would give you the same result, whether hardware or plugin VST!


At some point during the process, compression may be added (if required). Many people fall into the habit of over-compression, especially when mastering, but one of the main things you want to do as a mastering engineer is ensure that dynamics are preserved as much as possible whilst increasing loudness. Knowing how much to apply is not easy and takes a long time to train your ears for.

There can either be glue compression added across the mix to tame some harsh peaks and bring everything together, like the Cytomics The Glue plugin pictured, or a multi-band compressor like the UAD to (for example) restore some smack to the bottom end, calm down an overly aggressive snare, or restore some life to the top end of a mix with a hint of expansion.

Compressors all sound uniquely different and also add their own flavour of saturation to a track, both plugin or hardware e.g. tube.

Limiting & Finalisation

Finally, any last stereo width adjustments are applied before limiting and exporting the track.

A limiter is basically a finalising compressor, and allows for a final few dB of gain on the track to bring it up to commercial levels. If everything else is done right, you won’t need to push into a limiter too much at all. Some compressors allow for much more gain than others before driving distortion into the track, and it’s sometimes possible that more than one will be used to get the final result – i.e. one could add a touch of warmth, and another be very dynamic and transparent so work really nicely in combination in some applications.

As with everything there really is no set formula that can be followed as every single track will require a completely unique approach.

The main thing to remember though is with mastering less is more, and if a mastering engineer can achieve greatness with the tiniest of tweaks – then that’s the best possible outcome!

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