One major asset that all good mixes have in common is good separation. This is where all the many different things happening are clear and easy to pick out for the listener. So why do all the different sounds become so unclear and hard to pick out in the first place?
Resonance is one culprit. The resonating frequencies mask or blur other sounds occupying the same area in the spectrum. Also, when we hear sounds in the real world, the fact that they are all coming from different locations is one of the ways that the brain separates the sounds. When all the sounds are coming from a single set of speakers, some extra effort has to be made to allow the listener to separate all the different things going on.
This leads to an important point – depth. If effort has been made to give the mix depth then we are able to separate all the different sounds more easily. But before we get on to creating depth within a mix (not using Ultra Depth!), I’d first like to raise some awareness about the idea of separation and how it is so easily lost.
When two elements in the mix occupy very similar frequency ranges, it can become difficult for the listener to distinguish between the two. When a mix has many elements struggling to be defined, the mix may sound muddy, especially when it’s lower down in the spectrum. Throw in some unwanted resonance picked up during recording and the mix will become really rather stubborn.
Two sounds might occupy the same frequency range but have different textures, this would help them separate. Or, they might sit in different places in the stereo field which will help with separation too. Using the pan pot to separate sounds is good but you need to always ensure your mix sounds good in mono too, this is why EQ is an important tool for good separation.
Some advice I was once given was to start the mix in mono, get as good a mix as you can, then move to stereo. It’s important to understand that it’s okay for instrument frequency ranges to overlap but you still need to be able to tell them apart.
The tones of sounds can help with separation. Two sounds occupying similar frequency ranges could be EQ’d to have different tones or texture, one could be given warmth, the other could be brightened.
Muddiness can be the result of poor separation and is most often found in the low mids and lows, with the main culprits being the guitars and bass. A bass cab can create unwanted resonance. The room the bass cab is in can create resonance which tends to be more obvious in the lower frequencies down to the distance between the walls.
Electric guitars typically extend pretty low in the spectrum and on their own sound great, but all this low end causes trouble when adding the bass guitar to the mix as the bottom end of the electric guitar extends right down into the bass guitar’s range. Low cutting the electric guitar to allow space for the bass guitar will give much clarity to the low end. If you’re worried that doing this will make the electric guitar sound thin at times when it’s on its own, you can automate the low cut to only activate when the bass-line is present.
As mentioned in my book’s chapter on Expansion, even a little low cut to the bass to ensure the low end of the kick extends that little bit further down can help with low end clarity too. Or the application of a notch in the bass at a certain frequency can allow the kick to cut through. The very bottom of the spectrum doesn’t need much to fill. The kick and bass are plenty, and even they need to be separated from one another to some extent.
Pretty much everything in the mix, if played from a musical instrument, will have harmonics extending way up to the very top of the audible spectrum, and beyond. It’s important that you try to keep these intact as they actually help with separation. Whereas heavy handed cuts can help clarify the lows, gentle persuasion in the mids and highs should be all that is needed to achieve separation. High cuts can sound harsh and will affect important upper harmonics.
I hope I have managed to make my point… that separation is clearly of huge importance!
As just mentioned, creating depth in the mix helps with separation. Depth in a mix is when all the different instruments (vocals, guitars, drums etc) seem to have their own actual space, not just from a tonal point of view, but from a 3D point of view as well. All the sound might be coming from two speakers, but we can still give quite a good illusion that they are coming from different places in the room.
Depth can be achieved in many ways – EQ, reverb, chorus, panning and delays are all tools used for moving things around the sound stage. As I said at the beginning, I don’t intend to go too far into mixing techniques, I just want to get across the concept of good separation and definition.