A music theoretician might think tonal balance has to do with keys (tonalities) and modulations.
However, tonal balance (aka spectral balance) is related to the frequency bands and the overall balance across the frequency spectrum.
The aim of tonal balance is to have the energy spread across the spectrum evenly . This isn't to say that the aim is to have the same dB throughout - that would be white noise. The point is rather about balance across the spectrum and it's subsections.
A track will sound balanced if all frequency bands (especially the low end) manifest both fullness and depth.
What Would Tonal Imbalance Sound Like?
Any given track will show a certain level of tonal balance. Nuances will depend on the artist's preference of course, yet the right tonal balance will depend on multiple factors.
The relative tonal (im) balance will also depend on the genre. Some genres may use imbalance as an artistic effect at places.
To achieve the desired (typical) spectral shapes across the frequency spectrum. This of course is easier said than done.
Target curves are perhaps the most important for tonal balance, but a target curve isn't the same as tonal balance. It is just a projection; the "skeleton" of the tonal balance if you will.
When a target curve is established, as related to the typical spectral curves found in the given genre, the tonal balance and the balanced mix we are after are at least well defined.
In the mastering phase, the target curve will depend on the frequency range of the entire input. Now, target curves come in many shapes and forms regardless, which is why a visual analysis tool is very useful.
A great tonal balance is a mixture of serving the target curve and the entire spectrum (along with any particular frequency range, as necessary). High frequencies behave differently than lows, for example, and are likewise addressed in a different fashion.
Yeah... tonal balance isn't in the equipment, but you can't achieve one without it!
However, whether you're on one of the Apple silicon macs or any other operating systems/hardware combos, it really makes little difference nowadays.
Your favorite plug ins are compatible with most operating systems (if not all) in this regard. At the very least, one of each exists, which is compatible and does the job.
The Tools At Hand
Tonal balance is not preset in stone. Even if it were, at times you might want to make serious edits on the musical side. This in turn would call for additional tonal balance adjustments.
The Music Itself as a Tool
It's important to note that tonal balance adjustments don't need to always be applied across the frequency spectrum in its entirety. At times, some touches here and there will suffice.
Take for example the low end, in particular, the kick drum, as the frequency band represent. Typical spectral curves on the low end will depend on the balance between it and the bassline.
Tonal balance at the low end requires that the processing chain features a way to make space for the bass and the kick. Side-chaining is actually one way of improving the tonal balance in this regard.
Touching The Range?
To fine tune the tonal balance across the frequency spectrum, you might want to touch the frequency spectrum itself. The dynamic range may need to be adjusted too (especially the low end dynamic range).
Tonal balance can not be achieved with hi pass or low pass filters. They are instrumental in obtaining and sustaining a balance in the first place, however, at the very least for reducing muddiness.
Tonal balance can be achieved with the help of a few plug ins. With the most simple approach in mind, more often than not, an EQ plugin along with a simple compressor plugin should do.
You already have good plugins on your Logic Pro, FL Studio or Pro Tools (or any decent DAW really). So, whatever you're using for mixing and mastering is enough for the overall tonal balance to be achieved.
A spectral balance plug in would ease the flow further of course. The corresponding plugin window would typically feature a fairly accurate representation of the tonal balance at any given time.
Such a plugin can display factory target curves, mostly based on genre averages, which can then be customized to achieve detailed preferences (i.e. custom target curves).
Go Pro With High End Tools?
High end tools are not necessary in this regard. They require investments, which some aren't able to afford.
While the tonal balance of Duran Duran's "White Lines" was achieved with high end gear, it's worth noting that free plugins weren't a thing back then...
We've mentioned the dependence of the tonal balance on the target curves, which in turn depend on (or rather are defined by) the genre.
Commonly, as related to tonal balance, a genre will have a selected target curve range. When it is reached - more often than not - one can rest assured that tonal balance has been achieved.
Different styles don't mean different overall goals: at least not in the context of tonal balance.
The Natural & Artistic Surrounding
Popular music genres have distinct and well defined tonal balance, though it's important to always check how a track compares even to a track of an unrelated style or genre.
One thing to note here is that the impression will also depend on the listening environment.
A track will sound differently through your phone in the park. So, check if the tonal balance is established in another listening environment also (at least one more, apart from your studio).
The Human Perception, Practices, Limitations...
Music producers have their own ideas on tonal balance, just as they do about everything else.
One's tonal balance might feel weak to another... one's favorite EQ moves would be strictly avoided by another...
Whether an idea is actually a great idea will depend on many things. Yet, it's always good to hear a different perspective.
Yeah... tonal balance is tonal balance, but also: people are people. :) Always be ready to hear strong (and hopefully respectful) disagreements.
As a rule of thumb, most will first fine tune the low end through a number of EQ moves. This in an effort to adjust the crest factor, the "blue bars" and frequency areas to the target curve they're aiming for.
Next, the mid range is handled by making room, especially for the instruments/sounds which have a fast natural decay. This range gets easily overpopulated, so it's important for any "fog" to be addressed.
Next is the high register. The lowest frequency of a given sound is rarely placed in this part of the spectrum (apart from metallophones, of course). The job here is mostly related to deciding what to keep and what to ditch. Both extreme interventions and fine-tuning are seldom needed or called for.
Using a reference track does not mean to make a universal model out of it. Individual tracks will however bear their own sound; the spectral balance of a track can not be produced by a "recipe" of any sort.
Making comparisons to a reference track however, is a golden rule even for advanced producers. The sound of reference tracks at times is not only influential, but a game changer.
It is advisable therefore, that reference tracks are used; there's more to music and tonal balance than numbers and graphic representations.
As always, when you think your audio file is showing signs of having an optimal tonal balance - ear fatigue kicks in! :)
If and when uncertainty arises, remember to give your ears a rest! It's as important as the very process of optimizing the balance - if not more even, in the long run!
Take your time; your audio file might be already there. You may already have reached the tonal balance you're after.
Special Challenges as a Special Motivation
No matter how complex individual tracks are, tonal balance is achievable!
Without tonal balance, the artistic point won't be made, which isn't to say that tonal balance is an art form in it's own right.
Even if we want to represent imbalance through our music, the way to go would be to redefine and reinterpret what constitutes a (tonal) balance!
The Piece's Special Character
Apart from the genre context, individual tracks may manifest very special tonal balance control challenges. Achieving tonal balance is, at times, one of the most challenging parts of music production.
Some sounds' frequency ranges may be demanding and difficult to control, yet are crucial for the character of the track.
The tonal balance control interface (here in a metaphorical sense) will require that the frequency ranges of other less relevant sounds be adjusted accordingly.
Seek ways to refine the output of the crest factor meter, try to optimize the white spectrum curve, rebalance the low end's dynamic range.
The End Result
A balanced mix at its finest: unique custom curve developed, based on template target curves; higher frequencies tamed; master bus track optimized; tonal balance achieved.
A Rising Ambition
Satisfaction often gives birth to ambition, so you might start dreaming of more sophisticated spectrum metering information.
A greater mastering expertise will require purchase of a plugin which allows for a customized frequency bend definition, for example.
But even when you acquire what you're after, tonal balance is still not gonna be a given. Even defining the perfect target curve will still take some time.
A Few Notes in Closing
With mixing and mastering being an ever-evolving field, tonal balance might - and probably will - be reshaped and redefined in the future.
Gear will keep evolving, and so will your perception and intuition. Still, you won't need Premiere Pro CC to establish a tonal balance (obviously).
No One Knows It All
Even professional masters scratch their head sometimes, while facing tonal balance issues on their master channel.
A master producer might wonder why a touch in the bassline of the bass guitar significantly affected not only the tonal balance of the low end, but the overall tonal balance as well.
Let's Not Forget That...
Tonal balance depends on many factors, of which the listening environment is often neglected.
What works for one song might be off by a mile for another one.
A track's balance isn't in the plugin (even if it's unachievable without it).