If you're a music producer, feedback from clients, friends or other trusted ears is a hugely useful barometer of how close a mix is to being finished. But when analyzing their (hopefully) constructive criticism, it's interesting to note how you put their words into action. If you're a graphic designer and you show a client some work, it's not hard for them to say "that blue could be darker," or "that font could be larger." For producers, similar suggestions—"the mix could have more air," or "it could be crunchier"—are less tangible. Producers get better with experience at assigning meaning to these, but some are easier to tackle in a mix than others.

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.

Flat EQ: To help hear exactly what we're discussing, let's listen to different amounts of it in a whole mix. We've programmed a basic but deliberately lush track. Some of its parts, like the main melody line and the hi-hat, don't intrude into the low mid-range at all. But the bassline and a low pulse part are busy in this area, as are the lower notes of some of the pad parts, the bottom end of the snare sound and the main sequence. Here's the mix, with no EQ applied to any sound individually or to the output channel.

Low mid boost: The mix sounds reasonably well-balanced, if a touch overwhelming towards the bottom. Now let's hear how it sounds with the low mid-range pushed louder. Using FabFilter's Pro-Q in the output channel, we've applied a wide, 8-dB boost to the low-mids.

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.

Low mid cut: What does the same mix sound like with insufficient energy in this frequency band? Here it is again but, on this occasion, the same frequencies are being reduced by 6 dB.

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.

High notes only: Here are the two main pad parts from our mix, this time with their low notes muted the first time around. Even though the sounds are soft and dreamy, listen to how the low mid-range unnecessarily fills up as the chord progression plays a second time.

Low mid fundamentals: There's a third pad part in this track—a lower, monophonic part rich in harmonic content but with fundamental frequencies in prime low mid-range territory. Here it is, playing with the two pads as before.

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.

Recalibrating: To rein in this growling pad with those considerations in mind, we're using DMG's Equilibrium EQ. Like FabFilter's Pro-Q, this features an analyzer to help show the specific frequencies we're targeting. But this time, as well as applying a cut in the low mid-range centred at 157 Hz, we're also applying another cut below that at 63 Hz, to clear the bass register somewhat, too. Additionally, to accentuate the higher, raspier frequency content, we're boosting frequencies around 750 Hz, making this frequency band the priority.

Bass before: This has made room for the basses, which we introduce next. It's interesting to compare the original combination of the floaty pads and basses with the stripped-back and EQ'd versions. Here are those parts soloed from the original mix.

Bass after: Compare that to the same bass parts—but with our modifications to the pads restored. You'll hear how the bass parts now have more room to breathe.

Fixing the sequence: Adopting the same approach, we make an adjustment to the main sequence sound by scooping out some of the low mid-range before dialing in extra content to the snare part using EQ. This adds drive and power, and it bridges the frequency gap between snare and kick.

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.

Pure tone bass: In this clip, we've got a pure sine wave bassline sitting below a pair of quite thin beat loops and a rich pad sound. The bass works nicely when it's playing its highest notes, but when it drops down the octave, its low notes get a little lost. The sine wave nature of this sound means that there is no harmonic content to lend weight, leaving the low mid-range sounding empty.

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: We've substituted our first bass with a sound set up to behave as described. You can hear the bass play by itself for the first eight bars before the rest of the track joins in.

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.