Planes of Space in Mixing – Part 2

The following excerpt has been pulled in its entirety from Zen and the Art of Mixing:
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Planes of Space (Part 2 of 2)

In a stereo image there are planes of space that we use to create a four-dimensional image (the fourth dimension being time). All in all, I’ve determined that there are five basic planes of space replicated by two speakers: panning—left to right; frequency—up to down; balance—front to back; reflectivity—far to near; and contrast (dynamics)—sparse to dense.

Oops! Take me to Part 1!

Contrast—Sparse to Dense and Bright to Dark 

Contrast relates not to what is happening at any given moment, but to how the mix works over the course of time—the fourth dimension of your mix plane. Whereas we can listen to a mix and immediately hear frequency, panning, and balance decisions, we discover contrast decisions over the course of the mix.

Contrast is used to create the illusion of dynamics in modern music. By definition, dynamics is a variation in force or intensity, especially in musical sound. Unfortunately, dynamics in music has been greatly reduced over the years. Generally speaking, we’ve completely eradicated tempo fluctuations from modern music, and these days we don’t use much more than about 4 dB of dynamic range from the loudest to the quietest parts of a mix. In fact, the loudest mixes don’t even use that much range. While 4 dB may seem small, if you wish to hear the softer parts of your mix in the car, or while the dishwasher or vacuum is running in the next room, you’re not going to get away with using much more range than that. This means that we need to create the illusion of dynamic range, and we accomplish that with contrast.

When I mixed Ben Harper’s “Roses for My Friends” (from his third album, Will to Live), I originally sculpted an enormous dynamic range for the mix. The chorus was incredibly exciting because it was so much louder than the verses. Unfortunately, once I got the mix into my car, I found myself just tuning out until the chorus kicked in. What was an exceptionally effective payoff in the sound-isolated studio became a completely nonexistent payoff in the real-world environment of a car. Given this problem, we brought the verses up 2 dB in level during the mastering phase.

Now while we had to reduce the actual dynamic range of the mix in order for it to work in a real-world environment, the mix wasn’t by any means ruined. On this particular track, the dynamic range is naturally enhanced by the contrast in overall density between the two sections. The verse is sparse and sweet, while the chorus is dense and aggressive, so we get the illusion of more dynamic range than actually exists. That’s a good example of contrast providing the illusion of greater dynamics.

There are other ways to produce contrast. Suppose you have a single electric guitar panned hard left on the verse with no other harmonic part to balance it out on the right. Given this panning treatment, your mix during that verse will be wholly asymmetrical in nature. If a second guitar comes in on the right at the chorus, at that point the mix will have symmetry. The contrast between the asymmetrical panning in the verse and the symmetrical landscape in the chorus will accentuate the payoff and produce dynamics. Whereas the panning in the verse provides us with an unbalanced stereo image, the panning in the chorus provides us with a contrasting balanced image. But there’s more in play here than just contrast in symmetry. There’s also contrast in density. Implemented properly, density can make a bigger and louder chorus with more power and an intensified payoff.

To continue with our previous example, if we add a Rhodes in its lower register and place it in the verse opposite the guitar, we will now have stereo symmetry in the verse. This will greatly minimize the symmetrical contrast we had earlier—but where we’ve lost we’ve also gained. There is now a contrast in frequency that occurs between the dark Rhodes in the verse and the (presumably) bright, gritty electric guitars that take over in the chorus. It doesn’t matter where the contrast comes from, as long as it exists.

There will be times when you will need to manufacture contrast. Certain genres require the mixer to create the dynamics throughout the whole song. I’ve mixed many hip-hop tracks in which every part and sample played from the top to the bottom of the track, and I was completely responsible for creating an arrangement, contrast and all.

That said, contrast, while a definitive plane of space, is nothing more than a tool. Just as you can mix a song in mono, and thereby reject all that great stereo width, you and the producer can choose to use little to no contrast. How blatantly or obviously you use contrast depends on the track. Sometimes the contrast will come from the song itself. The more powerfully the song pushes you forward as a listener, the less the producer and mixer need to worry about contrast.

 Reflectivity or Reflection—Far to Near

Reflectivity is the illusion of space. Whereas we accomplish the three-dimensional illusion of width, height, and depth through panning, frequency, and balance, respectively, we accomplish the illusion of reflectivity within all three dimensions plus the fourth—time.

Sound exists within the context of its surroundings. We don’t just hear a direct sound source (unless the source happens to be right next to our ear); we hear sound within a certain space. A drum struck in a small room sounds completely different from the same drum struck in a hall, which sounds completely different from a drum struck at the precipice of a giant cavern. We perceive the sound and space by how the soundwave travels, and its reflections over time. The amount of time it takes for a sound to fully dissipate in any given space is called decay time. We all know that a large hall will have a much longer decay time than a small room, but in either case those reflections occur over time.

The decay time of any given room is determined by its overall size and shape, as well as the nature of the materials contained within the space. An empty large hall will have a considerably longer decay time than when it’s filled with people. That’s because people absorb sound, and the more absorptive materials there are within a space, the shorter the decay time will be. The more reflective surfaces there are in a space, the more the sound will bounce around.

Just as the contrast plane relates to time, so too does reflectivity. In fact, how we perceive reflectivity is defined mostly by decay time. For instance, the smack from a snare hit will travel through a room and reverberate. Depending on how big the room is, that reverberation will be perceived to occur some quantifiable amount of time after the snare is actually struck. We usually measure that time in milliseconds, since many reflections fully decay in under a second. There are 1,000 milliseconds in one second.

Reflections will appear to us as reverb in enclosed spaces, and as delay (with the possibility of some reverberation) in open spaces, particularly where there are obstacles nearby. While reverberation is the quick, successive bouncing of a soundwave throughout a space, delay is a singular reverberation caused by a sound traveling for a significant distance, hitting an object, and returning back to us. We’ve all experienced this kind of delay in real life; whether we are yodeling across a ravine (who among us can resist this?), or calling out to a friend near a large building, we perceive a one-time direct reflection from a distant object as delay.

We perceive space and distance based on both the quality and length of the decay. We also perceive our relative distance from a particular source based on frequency response and the ratio of direct source to reverberation. The more reverberation in the ratio, the farther away a sound source will appear to us, although one must also consider the context of the mix.

You can’t create the illusion of distance within a mix purely by drenching a sound in reverb. Internal balances determine the depth plane of a mix, and the relative balance of a sound must appear low in the mix in conjunction with the reverberation. Furthermore, since high end is so directional in nature, it will typically reflect and dissipate if anything gets in its way, so we can further enhance the illusion of distance by rolling off high-end frequencies from the sound source.

If you want to create the illusion of a dog barking way in the distance within a mix (don’t ask me why a dog is barking in your mix, just go with it), you would have to place it low in the mix, roll off the high end, and add plenty of reverberation. Putting the barking dog low in the mix places it back in the sound field, but the reverberation provides the illusion of distance, and the attenuated high-frequency response assists with the illusion.

Sometimes reflectivity is contained within a recording, as would be the case if you put a room mic on the drums. Sometimes reflectivity is added into the mix after the fact to create the illusion of a space that didn’t exist during the actual recording. Unfortunately, our control of reflectivity in a mix only works well in one direction. Whereas reflectivity can easily be added, it really can’t be taken away. Sure, we can use gates and mutes to cut off the decay at the moment a part goes tacit, but we can’t take away the audible room reflectivity while the part is actually sounding. This is why so many recordists use close-miking techniques when recording. When you consider the possible ramifications come mix time, it’s better to err on the side of too little space than too much. The best way to do this is to control how much reflectivity gets into the mic in the first place.

Personally, when I’m looking for the sound of “big” rock drums, I record them in a large space built with reflective materials (like concrete or wood, depending on how live I want the sound). In general, I prefer not to put off overall reflectivity decisions, as I’m not particularly fond of digital reverb. I’d rather have the real thing, if possible. Of course, that doesn’t mean I don’t take steps to give myself some control later.

Even close mics will pick up reflectivity from a large concrete room. Well-placed baffles and other deadening materials in somewhat close proximity to the kit can offer immense control over how much reflectivity is picked up by the close mics. In an especially live room, this can be a necessity if you want to have any control over the illusion of space. The room mics—which in this case would be far outside the baffle zone—are responsible for capturing the excitement and reflectivity of the room. This technique offers considerably more control in regard to how much (or how little) reflective information I can put on the drums come mix time. In this particular scenario the room mics act much like a reverb return (or a chamber), since they’re picking up the aggregate of the room reflection rather than the aggregate of the direct source.

As you can imagine, if you were to place the entire band in a large concrete room, things would get pretty messy rather quickly. Even if you were to record each instrument separately, one at a time in that large room, the reflectivity would be captured on every instrument mic. You would have no way of reducing that reflectivity later once it was recorded. This would tend to smear the overall sound to such a degree that the listener would have great difficulty making out the nuances of the performance.

If you’re provided tracks covered with room reflectivity, your hands are pretty much tied. There’s not a whole lot you can do about the number of spatial artifacts present in your mix. You’re resigned to deliver nothing more than a reverberant mess. To make matters worse, the moment you add a compressor to any part, you’ll merely bring up the reverberation of the room within the context of the source. Fortunately, most recordists and mixers realize the danger of this fairly early on in their careers, so you’re far more likely to get close-miked instruments without overbearing amounts of reflective information.

Recordings in which reflectivity has been harnessed are far easier for mixers to deal with than the opposite scenario. We have all sorts of digital reverbs and delays at our disposal to create the illusion of a space in the context of any given part. How much or how little reflection you choose to add to your mix depends on the song and production.

It’s not uncommon to mix and match acoustic spaces in a mix. For example, it’s rare to find crunch guitar or bass tracks recorded in a large room with an overt amount of room reflection. This is true even on tracks where a large room is used for the drum treatment. The listener is rarely offended by the reasonable use of mixed spaces, even though they couldn’t possibly encounter such a scenario in real life. The drums can sound like they’re in a large, reflective space, and the guitars can sound like they’re in an anechoic chamber, with no ill effect on the listener. This is really the only way we can create the illusion of a rock band in a large room without the resulting product sounding like nothing more than a smeary mess.

Still, you have to be careful about how you mix and match acoustic spaces within a mix. You don’t want to create a combination that is so foreign to the listener that it pulls them out of the mix. If, for instance, the entire band is recorded in a bone-dry, carpeted room, with little to no reflective information, and the singer sounds like he’s in an indoor basketball stadium, this could be a bit disconcerting for the listener. Flaunting your power to break the bounds of physics where acoustic space is concerned can serve to distract the listener and make them notice the mix. Remember, if the listener notices the mix, then it’s not a good mix. In the case of roomy drums and dry guitars, you’re creating a spatial illusion—one that listeners have bought into for a great many years. Therefore, it’s important to evaluate exactly what you’re trying to achieve when you address the spatial landscape of a mix.

If the singer is performing a song where the desired illusion is intimacy, then you’re certainly not going to drown her in a large hall. You probably don’t want any space whatsoever in that scenario. Intimacy is personal, and a personal performance would be done in either a living room or a bedroom (wah, wah, wah, wah!). If you want the singer to sound like they’re singing softly in your ear, then you should probably avoid any kind of reflection in your mix.

If, on the other hand, the singer is performing a dramatic ballad, then you’ll probably want the benefit of a soaring reverb and/or delay on the vocal, among other parts. This treatment not only provides the illusion of a large space (which makes the listener feel as if the song is being sung in front of the entire world), but the long reverb tail also accentuates the drama of the song.

In general, drums and percussion react well to reflective treatment, since short, percussive bursts don’t lose much clarity from the acoustic slap of a reflective space. Electric crunch guitars, on the other hand, lose all clarity within an overly reflective space. Sometimes that’s the desired effect, but usually not. Spring reverbs, plates, and delays are far more appropriate for electric guitars, and if they’re part of the amp signal, the player will adjust how she plays based on how the effect reacts. Violins become far less aggressive sounding in a large space, so this is a great way to soften the overall tone of the instrument. If the violin is supposed to be aggressive, then you don’t want a reflective treatment. If, on the other hand, the violin is meant to be soothing, then reverb is probably the best call. Singers are also good candidates for reflective treatment, although it’s important to consider the overall feeling of the track when choosing the size and decay time of the reflection.

In general, long reverbs tend to soften sound. If the music you’re mixing is aggressive in any way, then dramatic reflectivity can counter the desired effect. When you put a long, sweet reverb on a hard rock vocal, you instantly soften both the vocal and the production. Yes, hair-metal bands from the ’80s often used reverb, but hair bands don’t generally perform hard rock; they perform pop rock in the guise of hard rock. The whole point of using reverb on a hair band is to soften the tone to appeal to a wider audience. That’s not to say you can’t use reverb in hard rock (particularly if it’s nice and ratty), but you should consider exactly how that reflectivity affects the overall tone of the production.

How you deal with the spatial reflectivity in a mix can completely make or break a production. Too often mixers use reverb as a reflex rather than as a tool for manipulating the listener. Think of reflectivity as creating an illusion appropriate to the production. If the production works great with no additional space, then leave it as it is. If the production is in need of spatial illusion, add it.

Balance—Front to Back, Large to Small

Balance is a game of relativity and is the holy grail of the five spatial planes. I’ve left balance for last since it affects everything in a mix.

Fundamentally, the balance of an instrument has to do with how loud it is in comparison with all the other parts that are playing at a given moment. A loud vocal doesn’t exist in a vacuum. We deem it’s loud because it’s loud in comparison to everything else in the mix. All internal balances are merely an exercise in relative comparison. Balance is our most effective tool for directing the listener’s attention. If we make the vocal loud, the listener will tend to focus on it.

Every physical adjustment that we make in a mix is nothing more than a balance adjustment. A pan knob is a balance knob between speakers. Turn the pan knob to the left, and you’re turning up the level of a part in the left speaker and down in the right. Boosting or cutting a particular frequency is literally altering the balance of that frequency within the context of the part you’re processing.

Putting everything proportional in a mix will make for a shitty mix.

An overly balanced mix reduces contrast, neglects to offer the listener a clear focal point, and therefore reduces forward motion. Given this, a perfectly proportional mix does a poor job of manipulating the listener’s emotions. In other words, an overly balanced mix would be the exact opposite of a great mix, and this is without doubt a common mistake in mixing. It’s like a disease.

I’ve actually been thanked on more than one occasion for my “unbalanced mixes.” I don’t know for certain, but I think that would insult most mixers. I can assure you it’s meant as a compliment and taken as such. Frankly, there’s nothing more boring than a perfectly balanced mix.

Balance isn’t just about the relative levels within a mix. Balance also exists within the other planes of a mix. The louder a part is within the context of the mix, the bigger and more up front that part will appear. A loud, robust vocal placed smack in the middle of the stereo field (really, where else are we going to put it?) will not only appear more forward than any other part in terms of planes, but it will also take up the most space in the mix. Not only is it louder than the other parts, but it fills up the entire stereo field, and occupies a large frequency range.

The lower a part is placed within the mix, the smaller it will appear. While high-end frequencies have the energy to cut through the other parts, low-end frequencies need volume in order to generate energy. Therefore, a part placed back in a mix has an inherently reduced low-end push, particularly compared with the more forward parts in the mix. Low end and level are what make a part sound big. Reduce both of those relative to everything else in the mix, and that part will sound small.

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Zen and the Art of Mixing is the first book in my ongoing Zen and the Art of series. The digital versions (Kindle, eBook) contain loads of supplemental videos. You can purchase any and all of these books HERE.

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