Here, we'll dig into a frequency range that translates to what clients might call "weight," "power" or "energy"—the low mid-range. This slice of the frequency spectrum, sitting above the fundamental frequency of a kick drum but also below the main weight of snares, leads and sequence lines, can be problematic in a number of ways. So let's look at the role—both good and bad—it plays in mixes, to hear how our own tracks might benefit from some added attention to these frequencies.
First, let's define the specific width of the band. Like most things in music production, this is open to discussion, but for our purposes, we'll focus on frequencies between about 150Hz and 350Hz. The main reason this range deserves your attention is that it all-too-readily becomes overblown with unwanted content. Basslines, the upper harmonics from kick drums, the lower ones from pads and snares, sequence lines, guitar parts and plenty of other instruments all produce frequencies in this area. Often, though, these instruments are mixed to poke through in different frequency bands. If you're using EQ on any of these instruments, you might well boost at higher frequencies to provide clarity but leave the low mid-range flat. If lots of instruments have frequencies in this area left unchecked, it's very easy to leave your mix bloated and overwhelmed. However, the low mid-range isn't simply a problem that needs to be eradicated with dramatic EQ cuts on any instrument straying into this frequency bracket. It also provides essential energy that no great-sounding mix can do without, so we'll need to tread carefully to strike the right balance.
You can hear how bloated and overblown the mix becomes. What's particularly telling is how much energy is lost from mid-range and even treble frequencies. It's as if there isn't room for them in the mix.
The mix is now hugely lacking in energy and as a result sounds almost without foundation: the kick drum is attempting to provide weight at the bass end, and the absence of harmonic content in the low mid-range proves disastrous.
So we've now identified just how important a role low mid-range plays in a track. Mixed well, it lends the music energy, drive and purpose. Mixed badly and it will either overwhelm a mix or remove much of its power.
While global EQs are useful, let's focus on individual sounds, identifying those playing a useful role in this frequency band and those which could be adjusted to improve the mix overall. First, let's listen to some sounds that are unintentionally filling up the low mid-range. When you're recording pads, for example, it's easy to hold down fistfuls of notes, as it's a natural tendency to play with both hands on the keyboard at the same time. But are you actually including the pad sound because you like how it sounds higher up the keyboard? If so, muting or erasing lower notes—which are cluttering the low mid-range—will make space for other sounds.
With the basses still to be added, this part hasn't been designed to be the engine room of the low mid-range; its upper harmonic content is what provides some pleasing bite.
Of course, the same considerations need to be taken to low mid-range content regardless of the musical genre you're working in. Let's look at a drum & bass example. When combining beats with basslines, pure, almost sine wave basses are favoured by plenty of producers. However, there can be a pitfall to this approach: it can leave a hole in the low mid-range altogether, meaning such bass parts don't glue to brighter mix elements.
We can counter this problem by swapping the pure bassline for a sound with more harmonic content, using a trick to retain the purity of our previous tone. If you employ a low-pass filter on sounds with greater frequency content, you reduce the richness of those harmonics as it closes. Using an envelope on a bass sound so that it produces a momentarily frequency-rich punch at the beginning of a note before dropping to produce a purer sound for the sustain portion can produce a great result. The attack fills up plenty of low mid-range, providing the energy and power we're looking for.
Envelope shaping of the filter can prove hugely useful. Interestingly, the opposite—tones starting with a very pure sound that then open up into the low mid-range—can work well, too. This is part of why dubstep wobble basses have become so popular. Think about a single cycle of such a bassline: the filter opens from closed to open and back again, effectively lighting up bass, low mid and then mid-range frequency content before shutting it all down again. During the note interval of your choice, such sounds therefore glue bass to mid-range together via the all-important low mid-range band over and over again.
So regardless of the music you produce, think carefully when addressing low mid-range. At the very least, put an EQ in the output channel to check whether this area has become bloated or, conversely, too thin. After that, address individual sounds in your mix to remove unneeded notes before paring back or boosting low mid-range frequency content on sounds using EQ. Think too about the design of those sounds and how you can shape them to ensure you've got the right amount of energy and power in your mixes. They'll sound all the better for it.