As I might just have mentioned once or twice before, there are no special mysteries in mastering, mainly just fairly common issues in real-world sound scenarios – including real-world irritations – and fairly straighforward ways of overcoming them.
Here’s a real-world example of a common EQ problem. I was sitting in the PBM monitoring chair, not working but listening attentively and happily to a classical piano music CD that was released a few years ago. It was something slightly irregular – Berg’s sonata – and so required a bit of concentration, and I was listening both for pleasure and to see just how well (or otherwise) the recording engineer (me, in a previous life) had managed to capture the full dynamic and frequency range of the instrument. A few minutes into the piece I was feeling quite content.
Behind me my assistant, not really much of a classical music enthusiast, was sitting at the DAW, doing some computer housekeeping and listening quietly on in-ear speakers to something entirely different. I could not hear what it was – that would have been an irritation of an entirely different order – but it was clearly something catchy because after a while he began gently to hum along with it. Naturally (I assume that everyone feels the same way) I found this a tad distracting and irritating – it meant that I had to consciously concentrate, even to strain a tiny bit more in my listening. I became discontented. Finally the irritation peaked when his harmonically invariant humming became just loud enough to prevent me from hearing some of the subtleties of the piece – ppp middle register notes – notes that I really wanted to check had been decently captured. I had the score with me, so I knew they should be there, but at the critical moments the low humming from behind me was just enough, and in just the right frequency range, to mask what I was listening out for.
Here’s a real world example of how to solve that EQ problem: I tapped my assistant on the shoulder, firmly enough to indicate my displeasure. He jumped a bit, looked at me, mouthed “sorry” and shut up. When I turned back to listen the piano recording could immediately be heard much more clearly again, and I could confirm that the previously hidden notes that I’d hoped were going to be there, were.
When the mastering aim is to clarify upper mid-range textures, the effective use of EQ is sometimes simply a matter of stopping something nearby in the mix from `humming’ in the lower mids. This can be a single item – for example, upper bass notes which ring a little too long, or the lower strings of an acoustic guitar, can muddy up the low end of a male vocal – but it can also arise when a number of instruments in the mix have overlapping frequencies in the same critical region – as can easily happen with acoustic ensembles, from string quartets to folks bands. The mastering skill, as in all EQ practices, is then just listening to identifying that region, and then knowing how much to cut, and how broadly. Simples …