As previously defined, the low-mid portion of the audible spectrum runs from about 300 Hz to 600 Hz and contains mostly the fundamental frequencies of non-bass instruments.  This is the comfortable middle range for vocalists, the standard range for guitars, horns, strings, and other instruments.

It also is the range where the first few harmonics for the lower frequency instruments sound and give character to those instruments.  In more sparse mixes, these upper frequencies can be altered to help separate the bass from the kick and so on.  However this is also where a lot of build up will occur due to orchestration, so don’t bank on these frequencies helping to bail you out in dealing with the bass problems in a dense mix.  I’ll speak more at length about harmonics and how they can help you in next the mid-frequency article.

For the voice, most of the power and audibility comes in this range since it is the portion that contains the distinct vowel sounds which vocalists latch on to.  While this is an important range in dialogue and speech, it is also vitally important in music since vowels are what allow singers to elongate words.  Think about it, when you want to hold out a syllable, it is almost always the vowel sound that is held out.  It’s pretty difficult to lengthen a P or D sound.  Holding out an S just sounds sibilant.  So for clear vocals, it is pretty important not to muck up this frequency band.

This is easier said than done.  A lot of indie rock musicians have problems with this range.  Being a self-professed indie rock snob, I say this without any intended slight:  most indie rockers are not necessarily the most virtuosic musicians.  You can hear it in Caleb Followill’s vocals and Nick Drake’s guitar playing and Meg White’s drumming.  It isn’t that they are bad or they don’t write good music.  I love their music and they get the point across.  Let’s just say they aren’t necessarily in the realm of Yo Yo Ma or Mozart.

The truth is that most musicians who don’t perform a bunch of acrobatics like to stay squarely in this “comfortable” range when playing and that can really cloud the mid-range in a song.  If an untrained keyboard player lays down a keyboard track, changes are they’ll circle middle C.  And weaker vocalists might also stick in this comfortable range as will guitar players and trumpeters and string players, etc.

That’s another reason why solo musicians doing all the tracking themselves at home can struggle with their mixes.  They know that the bass is played way down on that end of the midi-controller and everything else kind of sits in this middle range.  If you are using midi for everything, then most people will play all their midi instruments in the same way. 

Being in studios for so long, you start to develop a knack for feeling out musicians.  Horn players behave like horn players and therefore sound like horn players when they play.  Drummers behave like drummers and usually sound like drummers when they play.  Singers and string players and harmonica players and everybody else roughly kind of act in the same manner and have a certain personality that is evident in their playing.  If a horn player is programming all the different instruments on a midi keyboard, he might find himself in a rut because all the instruments are playing parts like a horn player would instead of all these different personalities bouncing off each other.

The upshot is that if you are doing everything yourself at home and you aren’t well versed in orchestration or how certain instruments sound and play and how they do that in relation to other instruments, you might end up with a big pile of mid-range instrumentation that obscures the vocal as well as the other instruments.

So it is important to bear this in mind while writing and try to compartmentalize various parts to certain parts of the frequency range so that they don’t interfere with each other.  Keep the horns high and the guitar low and the vocal all by its lonesome.

Of course this isn’t always possible, so to address it you might emphasize certain frequencies in this band in some instruments and not in others.  For instance if a guitar is playing rhythm chords and a piano is chucking along as well, you might boost the guitar at 450 and then do the opposite in the piano.  This doesn’t need to be a drastic EQ, just enough to relegate each instrument to a certain portion of the range.

Much like the bass, we are dealing with a limited range of frequencies to do that with, so you might also want to try treating the upper harmonics which will give you much more room to play with.  These will come into play in the next portion of the audio spectrum:  the mid-frequencies.