From Zen and the Art of Mixing:
© All Rights Reserved
Every balance decision that you make affects the mix in an equal and opposite manner, particularly as it relates to what comes next in the song.
You should always think of balance in purely relative terms. Setting aside the complicating factors of the stereo bus compressor, if you bring up the drums, you’ve also essentially brought down all the other parts. If you bring up every part but the vocals, you’ve pretty much brought down the vocal.
Relativity also exists between sections. Whatever is currently happening in a mix serves to set up what happens next. The push and pull of balance is the fulcrum you use to manipulate the listener forward. If you bring the entire verse up 1 dB in overall level, the listener only perceives that level change relative to the sections before and after it. If you bring up a simple snare fill before a chorus, you’ve effectively added an exciting push forward for the listener. But if you bring that snare drum up too much, you can actually weaken the entrance of the chorus by making it seem small in comparison.
You should give as much weight to how a balance decision affects the current section as you do to how it affects the next one. Two electric guitars blaring from the top to the bottom of a mix do little to enhance contrast. Bringing down the relative level of the guitars in the verse would be a reasonable solution to the problem. While the timbre of the instruments won’t change, the level difference will provide you with some contrast. Muting one of the guitars might prove even more useful for promoting forward motion and payoff. Or you could let the mix just be static, but if that’s your decision, the song better have plenty of forward motion on its own. Otherwise your mix is going to fall short. Just because the songwriter and the producer ignored the benefit of a good payoff doesn’t mean you should. Someone needs to stop the insanity—it might as well be you.
Suppose we have an egg shaker on a rock production that plays relentlessly in the verses. An egg shaker can wreak havoc on the payoff of the chorus, particularly if it stops once the verse ends. It doesn’t really matter how great the egg shaker works in the context of the verse if it ultimately destroys the chorus payoff. This is far too great a price to pay. I use this example because shakers, particularly egg shakers, which contain mostly high-frequency information, can be difficult to bring in and out of rock mixes, as they often have the undesirable effect of causing the guitars to sound dull when they go tacit.
These are extremely broad generalizations, and I’m a bit reticent to provide more. Not every shaker will dull every track, as that’s frequency-dependent on both the overall program material and the shaker itself. You can make an egg shaker far louder on a sparse R&B track than you can on a rock track. That’s because the basic sonic landscape of an R&B track tends to make less use of the midrange than your basic rock track. Shakers don’t cause the low end to sound dull in contrast. Shakers dull parts that exist in the upper midrange—like guitars. Not so with tambourines. You can bring those up as loud as you like.
Relativity affects everything in a mix. If you bring up the low end on the bass, you risk making the kik sound too small. If you place a big, beautiful acoustic guitar on top of a gritty rock band, you could very well dwarf the drums. If you pack a mix with parts in the upper midrange, you’ll probably be forced to place the vocal exceptionally forward in the mix, as all those midrange parts will compete directly with the vocal.
Each and every balance decision causes an equal and opposite balance reaction, both in real time and in what lies ahead.
I could go on for hours with rhetorical examples of balance decisions that can potentially affect other balance decisions, but the specifics aren’t going to be of much help. From a pure process perspective, balance decisions are the lion’s share of mixing. These sorts of interdependent decisions are made constantly throughout a mix. But if you start to think about your balance decisions based on how they affect what comes next, you’ll have a far easier time achieving an effective mix in terms of the big picture.”