When discussing good frequency balance in the mastering process we must first set out our basic aims and contextualise their affect on the other parts of the process to understand the most effective way to correct and/or enhance the session mix.

To achieve a mastered sound we need good tonal balance, meaning, to make a track ‘fit for purpose’. It must sound equally weighted within itself on all playback systems. This could be a hi-fi, car stereo, i-pod, mobile phone, sound reinforcement rig and so on. This balancing is also the key element in achieving perceived loudness in a given mixes dynamic range.

When first listening to a session mix I’m interrogating the following differing aspect of the tonal balance;

  1. Is the composition of instruments individual tone within the mix in equilibrium?
  2. Is the proportioning of bass (LF), middle (MF) and treble (HF) in balance?
  3. Are there any tonal resonances or holes?

In example; We could have a track that is dull, lacking high energy overall, but the instruments interact well between themselves, being equally as dull as each other. In this we would only need to apply a small tonal shift to make the track ‘fit for purpose’. This type of mix we would describe as well balanced even though the proportioning of relative tone is not.

In another example, perceptively the tone overall may sound in balance but within the instrument interaction the amount of presence of the vocal is masking the actual amount of treble in the mix. This is quite common where the mix engineer has not reduced the sibilance on the vocal enough and because of it presence they have not equally addressed the tone correctly in the rest of the mix. This type of mix we would describe as in need of corrective tonal balancing.

Another common issue is if the mix sounds generally in tonal balance apart from the low end woofs from around 50-60hz down. This is a common problem with mixes constructed on small near field monitoring and/or where there has been little attention to correct use of filters (see other article). Again, this type of mix we would describe as in need of corrective tonal balancing.

An interesting issues with rock mixes is where there is good tonal balance throughout, essentially an excellent mix but the attack/snap of the snare and/or kick transient is to aggressive, masking the other high mid content making small tonal correction to the high end unproductive. This will have been because the monitors used did not translate the percussiveness of the transients correctly. Lack of fast transient detail in studio monitors is common. The mix again we would describe as in need of corrective processing before the small tonal balancing required.

We always have different aspects to address, every composition, album and artist is unique. The correct tonal balance is relative to the intent of a track but we can split differing events in to two distinct categories - Corrective and Tonal balancing.

Corrective will always be before tonal balance as until the mix is equal within itself we cannot equalise its tone overall effectively making it ‘fit for purpose’.  These to distinct stages should not be blurred.

The correct tonal balance is relative to the intent of a track but we can split differing events in to two distinct categories - Corrective and Tonal balancing.
— JP

In corrective, we are dealing with issues within the mix that have not been picked up in the mixing processes. These could include; honking or resonate bass notes, middle range resonances/holes, over zealous hi hat/cymbal and/or ‘s’, ‘t’ on vocal. Any and all of theses need to be corrected or balanced before we can start to address the overall tonal correction of a mix.

We would engage in corrective processing mainly through the use of a linear phase EQ or via dynamic tools such as a linear phase multi-band. This, in affect, is EQ because if we change the gain of a frequency band dynamically we are inherently equalising. A linear phase tool would be the first choice as we can be extremely corrective with minimal artefacts in relation to more traditional tools. Tool types we’ll discuss in a separate article.

At this point it should also be pointed out a multiband compressor/expander is only needed because the mix is lacking. In nearly all cases a better result can be achieved by the issues within the mix being addressed by the mix engineer under direction or if stems are provided instigating the correction on the individual stem thus avoiding unwanted or ‘artefact’ of the correction on other parts of the mix. Again, stem delivery and uses we’ll discuss in another article.

Obviously not all situations allow for this but if it is possible we should make our best efforts to acquire a corrected mix version before mastering. After all, everybody involved in the chain of process should be interested in one thing - Making the final product sounds as good as possible.

An important point to take on board regarding the use of a multiband is; it’s being used to correct and not to make the track perceptively louder. Perceived loudness comes from good tonal balance and correct use of full band compression, not from a multiband tool. This is general misunderstanding and preconception of the tools used to create a good ‘sound’ in the mastering process. An excellent master comes from an excellent mix and the use of appropriate mastering tools.

Other methods for corrective processing involve the application of Mid/Side (M/S) to apply multiband dynamic/EQ to more localised areas of a mix though, by its nature this is still not as ideal as stems or going back to the mix but is still a very effective method where we cannot go back.

Understand linear phase tools work well in general when engaged in corrective processing doesn’t mean we should ignore other avenues. In practice, trusting your ears as always the best method, if it sounds right then use it though it’s important to try to understand why a tool or set of tools has been effective in that situation as we can use that learning again at a later date. If you evaluate tools and their processes it will help you to make the correct choice first time, more of the time.

Once corrective tools have been applied to address the issues we can get down to correcting the overall tonal balance. This firstly involves being able to correctly hear what needs to be corrected. Without saying, understanding your monitoring is vital in all aspect of tone, panorama and depth of field. A small amount of EQ 0.5db is the difference between a clear ‘fit for purpose’ master and a dysfunctional one. In mastering we are concerned with small, but crucial tonal shifts. These may, in many cases, not even involve EQ but dynamics to make the tonal shift by the manipulation of the envelope. This is again inherently EQ, if we change the shape of a transient we change its tonal character. I would say in practice with a good mix the mastering compression has more of a role to play in tonal shift rather than EQ. This in general cannot be achieved with mix compression, mix tools are too aggressive for the overall mix. In mastering we are interested in enhancing a good mix and not remixing it!

If you want to make your mix sound truly mastered you need to put it through mastering quality equipment. Not just because it makes the songs sound great but more importantly it makes music sound right on all systems. Those tools might differ but you’ll find all mastering engineers worth their salt are using mastering tools such as GM, Manley, EMI, Weiss, Crane song, Maslec and so on. Not mix tools such as SSL, Neve, API, as they are for a different application. All of which will be outboard, not because mastering engineers don’t like digital but because if you want to achieve a tonal shift in a mix, 99% of the time a piece of quality mastering outboard with do the job 100% better than a digital equivalent.

If you want to make your mix sound truly mastered you need to put it through mastering quality equipment.
— JP

Mastering is about finites - mixing is about producing the emotive translation of the song. The outcome from both done well should be a great sounding record.