What makes a great song? Is it a matter of fashion and taste? Or are there set rules for quality? Could it be a little bit of both?

These questions have always been really fascinating to me. In particular, I have been really intrigued by the idea of finding the parameters of a great music mix. If you ask ten people what makes a good mix, you will often get ten different opinions, and yet, it seems as though there are certain things that all great mixes have in common.

The idea of defining a good mix is so fascinating to me that I am doing a PhD on the topic. So what did I find out? Excitingly, there are certain parameters that all great mixes have in common! I even managed to find several computational predictors for one of them (you can read one of my papers here, but be warned, there is some maths involved ;)). Many more years will pass before computers can mix any piece of music perfectly, but tools like Landr prove that it’s indeed possible. Today I want to share with you my research on the parameters of a great mix.

Here’s what I did. I read around a hundred books, articles, blogs and so on. Some were scientific studies, others were written by producers, again others by prosumers. I made a list of all the terms I could find. If you love a good word cloud, have a look below! I can tell you now that no researcher has ever before come up with a conclusive, whole list of all the important parameters of a good mix. But there were five parameters that kept popping up again and again — and all the words in the word cloud fit into them. Read on to find out more!

1. Clarity and separation

Clarity and separation is the extent to which sounds can be heard in a mix. The important characteristics (e.g. timbre, groove, melody etc.) of individual components, especially lead and vocal sounds, need to be clearly audible (and sometimes exaggerated) for a mix to be perceived as clear and separated. Owsinski, author of 23 books on recording, music production, the music business and social media has asked several iconic mixing engineers, including Ken Kessie and Kevin Shirley about what makes a great mix. Both strive to create a present, bright and clear vocal. Clarity is related to loudness because the louder a sound is, the better audible it will be. But bear in mind, not only turning up the volume knob makes sounds louder, often it’s clever equalisation (of the sound in question AND the sounds that surround it). Have a look at loudness and masking if you want to find out more.

What’s interesting is that while clarity is really important for some sounds, others seem to benefit more from a little bit of ‘glue’ or ‘blend’. Getting the balance between blend and separation right is the important bit here. For example, while a Gregorian choir piece might sound great blended, without any of the voices sticking out, a heavy rock recording might be judged on the clarity of vocal and drum sources, and the way that the bass and guitar work together spectrally. Bob Clearmountain, the king of the Rock’n’Roll mix, always ensures that the drums blend well with the bass (read more here). Blend can be achieved through bus and mix compression for example. So, overall, the important characteristics of some sounds need to be clearly audible while other tracks may benefit more from being blended together.

2. Balance

Balance in general describes an even distribution of energy in the spatial and frequency domains. So what does this mean? Basically, we are looking for level, tonal and spatial balance. In other words, you could describe a mix as having three dimensions, height, width, depth. Producer Bobby Owsinki calls these three dimensions “tall, deep and wide” and Rick Snoman, author of the multi-award winning and best selling textbook, “The Dance Music Manual”, calls them “harmonic balance”, “stereo balance” and “depth”. Read on for some more info on the three dimensions of balance: horizontal balance, tonal balance and depth.

Horizontal or stereo balance is the extent to which, within any given frequency range, sound energy is distributed symmetrically and “evenly” between the left and right channels. This essentially means: no holes, lumps or asymmetries anywhere in the stereo image! But… people disagree on this a little bit. Mixing engineer Dave Pensado describes hard left or hard right as “sacred/noble territory” that should be used sparingly ( read more here) but interestingly, this did not seem the case in a recent scientific study by Pestana and Reiss [2014]. In either case, it’s important to give stereo balance a bit of thought if you are striving for a great mix. You can do this by panning sounds or by using stereo effects (try doubling a sound with a copy that has a tiny delay and pan them left and right, if you haven’t yet! It sounds phat indeed)

Depth is a sense of perspective in a mix, where sound sources can be placed at various distances from the listener and inside a fictional, reverberant space of a certain size and shape. So, think foreground and background. You can do this by e.g. adding reverb or equalizing sounds (did you know that low frequencies can travel around objects, while high frequencies are better audible from a distance? This gives you clues as to how to EQ sounds for depth)

Tonal balance is the extent to which sound energy is distributed “evenly” across the frequency spectrum: according to Bobby Owsinski, mixing engineers often adapt the frequency spectrum to a reference point whilst trying to achieve a “high fidelity” sound. More recent studies confirm that although every song is unique in their spectral/timbral contour, there exists a target equalisation curve that stems from practices in the music industry but also seems to mimic the natural, acoustic spectra of ensembles. Pestana et al. [2013] explain that spectra of professionally produced commercial recordings show consistent trends, which can roughly be described as a linearly decaying distribution of around 5 dB per octave between 100Hz and 4000Hz, becoming gradually steeper with higher frequencies, and a severe low-cut around 60Hz. Huh, what? In other words, make your overall spectrum have a similar shape to pink noise! You can do this by equalizing individual sounds or the whole mix, and also by making sounds with differing spectra louder and quieter.

3. Impact and Interest

So, we have a balanced, clear mix. But what’s missing? It might still sound boring! Impact and interest is the extent to which the mix grabs the listener’s attention. Think exciting, artistic, powerful, dynamic, imaginative, punchy, loud, contrasting, surprising, larger than life, etc. There are many ways that this can be done, but compression certainly plays a part in this. And so does contrasting treatment to different sections of the song!

Academic, author, composer and record producer Zagorski-Thomas says that “if, at a subconscious level, the perception of music involves hypothesizing what it would feel like to produce that sound, it would be useful for both music and musicology to study the grey area between edited performances that are perceived as possible and those that are perceived as impossible or unnatural”. Impact and Interest basically.

4. Freedom from technical faults

A good mix should be free from technical faults! This means, no hum, pops, clicks, unwanted distortion, recordings that have obviously been made in an unsuitable room, etc. This is an easy one! Mixing engineer Dylan Dresdow says that there should be “no artefacts or horrid tuning”. Of course, there might be some mixes where you’d want some “dirt”, but in general it’s better to avoid all of the above.

5. Context

OK, now we have the recipe for a perfect mix… or do we? I will admit, that there are some things that cannot be generalized. A mix fits into its intended context when it conforms to current trends, fashions and norms, complements artistic purpose of the recording and supports the musical content. These things can change over time, differ between artists and depend on the situation.

Here are some interesting thoughts about context. The Flying Lizards’ 1979 single “Money” is deliberately mixed to sound thin and weak to fit the song! No balance, clarity and separation or impact/interest! Roey Izhaki, author of what I see as the bible of mixing, writes: “a mix can, and should enhance the music, its mood, the emotions it entails, and the response it should incite”. And that’s different for each song, right?

Did you know that Queen inscribed “no synthesizers were used in the making of this album” on their early records? And that Brian May made multiple layered guitar track mixes at the same time? Why was one use of technology perceived as unauthentic, and the other was not? All this is clearly to do with fashion, taste and opinion.

The books that provide mixing tips usually admit that there are no perfect settings, no magic presets and no hard and fast rules that lead to the perfect mix. Partially, that’s because a mix that makes one track sound clear, balanced and interesting, would make another sound dull, lopsided and boring (e.g. the EQ settings that make my voice sound clear, will probably not work for your voice, because your voice is not my voice!) But at the same time, mixing does have a creative side that cannot be automated. For example, there seem to be different schools of mixing where some engineers prefer a hot lead vocal while others tuck the vocal lower into the mix. Bobby Owsinski mentions the “London style” or the “LA style” of mixing which he relates to the use of the iconic technology available at each location respectively. Bill Gibson, author of more than 30 books, points out in “the Art of Mixing” that the musical style, song, details and people involved, as well as the mixing engineer’s own taste and the taste of a mass audience will have a strong impact on the final product (check out his cool visual representations of imaging here).

So what’s the conclusion?

All in all, a variety of factors such as fashion and taste, as well as characteristics that are specific to individual pieces of music can have an impact on what is perceived as a good mix. These make it harder to generalize values of a good mix or to even automate the mix process. But as we have seen, there are indeed some parameters that all good mixes have in common and these are clarity and separation, balance, impact and interest and freedom from technical faults. So, happy mixing! Oh, and before I finish, here is a nice picture of all parameters of great mixes.