Who is really responsible for a fantastic sounding master? Mixing is justifiably a bigger subject than mastering and would easily fill a book or two by itself.
For that reason, rather than give a tutorial on mixing, I am simply going to outline some of the most common problems I have come across when receiving mixes from clients.
I won’t go into too much detail with things like, what frequencies to boost, or cut to improve the mix, or any other mixing tricks. I’m just going to try and get across an overall concept of why some mixes produce good masters and why others don’t. In doing so, I hope to shed a new light on this massive subject.
In a perfect world, all the problematic mixes I receive will go back to the mix engineer with a report on the issues I have found, followed by a remix, and then a great sounding master. The truth is, sometimes I have no choice but to make the best of a bad situation and master, to the best of my ability, a problematic mix. Having mastered many problematic mixes I am able to give some advice on why certain mixes don’t produce the best results, and why others do.
Mixing Sounds Together
There’s a fundamental rule when it comes to playing different sounds together at the same time. The lower down the spectrum the sounds lie, the more difficult they are to blend together.
I use a bass guitar playing two notes simultaneously as an example. If you play two different notes way down at the bottom of the bass guitar’s range then the two sounds will not sound clear, or very musical being played at the same time. Play the same two notes a few octaves up and all of a sudden it’s not so unpleasant to the ears hearing these two notes.
It’s unlikely in any song that the bass player will be playing more than one note at one time, but there are other factors that can cause there to be more than one thing fighting for space in the bottom end of the frequency spectrum.
Occasionally, I will receive a mix where the choice of kick drum is that of the tuned category. By that I mean, will have an obvious frequency or musical note contained within the kick’s sound. These are usually synthesized kicks or sampled (a natural sounding, and correctly recorded acoustic kick should not have any obvious tuned frequency or musical note).
When a mix contains a tuned kick, problems can occur as the note usually clashes with that of the bass-line. These conflicting frequencies at the very bottom end of the spectrum cause it to sound unclear and muddy. Tuned kicks have their place. In house styles of dance music, tuned kicks can sometimes be quite suitable so long as effort has been made to ensure the kick and bass-line work together.
Another rule is the more natural each sound is – as in how well recorded – the more easily they will mix. If when you record the sound of an acoustic guitar, the mic picks up some undesirable resonance of an untreated room causing certain frequencies to resonate, then this guitar may well be stubborn during the mixing stages.
When listening to a musical instrument in the real world, you would probably not notice room resonance unless you have a trained ear. To effectively record a musical instrument, you need to avoid placing the mic inside areas where the room is causing certain frequencies to jump out. Poor microphone placement will force the mixing process to be quite difficult.
A musical instrument itself may cause certain frequencies to jump out a little when the mic is placed close in to the body of the instrument. The resonating body of a musical instrument is how it produces sound in the first place, but there has to be some distance between a microphone and the instrument for it to sound correct. Only once the sound has travelled a certain distance away from the instrument will it form the natural sound of that particular instrument. Depending on what part of the instrument body you point the mic at, you will get a different sound. Some areas will be desirable helping you towards a nice mix, but some will not and will cause trouble.
A good mix starts here – microphone choice, microphone placement, suitable room, good musicians. If you get all this right then the mixing becomes much easier. You end up needing much less processing like EQ to persuade the mix to, well, mix.
When using the EQ technique described in my book, The Audio Mastering Blueprint (sweeping a boosted EQ across the spectrum), these undesirable resonant frequencies picked up by poor microphone technique are one of the things you are looking for. A very good mix will reveal little, or no unpleasant resonant frequencies when applying this technique – this is the best result you can hope for.