Before there was digital recording, before spring reverb, even before analog tape, there was EQ. Equalization is one of the oldest tools in the audio engineer’s arsenal, and one of the most useful.

Used judiciously, EQ can do wonders to de-clutter a crowded soundscape. Used with precision, it can remove offending sounds we hadn’t necessarily intended to capture. Used correctly, a bit of EQ can be all that’s needed to make peace between dueling guitars, scoop the mud from the heaviest drums, or make a mundane vocal stand up and shine.

But all too often, EQ is misused and misunderstood, typically in a vain attempt to fix a poor recording.

Rule Number One in recording still applies: garbage in equals garbage out. A little EQ is great for helping make a good track sound better, but no amount of EQ will make a bad track sound good.

The best mix starts with the best recording, so try to capture the best sound you can to begin with. Move mics, listen at the source, not just in the control room or in your headphones. Make sure what’s being recorded sounds as close to what’s being played as possible – before it’s too late to do anything about it.

Your ears are the bottom line when it comes to applying EQ. While we can talk about a few general principles, every instrument has its own unique characteristics and timbre, and will react differently to boosting or cutting specific frequencies. So take these and all suggestions with a few grains of salt; use them as a starting point but make your decisions based on what sounds good.

EQ Giveth & EQ Taketh Away

When it comes to EQing, less truly is more, and in nearly all cases it’s better to take away than to add. Many less experienced users have a tendency to make an instrument stand out by boosting frequencies, but the cumulative results can be dangerous.

Adding just 2 dB of gain to two different instruments means that when they excite the same frequencies (and trust me, they will, and probably at the worst possible moment), you’ve got 4 dB of gain. Add too much EQ and your mix can easily turn to mud. It’s often a better idea to try attenuating those same frequencies in other instruments instead.

Another good reason to minimize your use of additive EQ: while cutting frequencies is a passive process, boosting frequencies makes your EQ function as a preamp within the signal flow. Adding any preamp means adding noise and distortion, and the preamps in most EQ circuitry are less than optimal.

All those arguments aside, sometimes it’s simply more effective to boost one element of the mix, rather than rolling off dozens of others. Once again, the operative word here is moderation – a little boost of 1 or 2 dB goes a long way.

EQing Drums – If It Doesn’t Fit, You Must EQ It

If your mix includes drums, it’s a good bet you’ll spend a considerable portion of your mixdown time EQing them. Because drums cover such a wide tonal range, there’s plenty of other stuff in the mix that can compete with those frequencies. Kick and snare in particular tend to be prominent parts of the song’s sonic fabric, and when it comes to helping them play nicely with other instruments and vocals, EQ is your best friend.

Of course, assuming you’re working with a live drum kit (as opposed to isolated drum samples), you’re not working in a vacuum. Since every drum track also contains leakage from other mic, boosting a frequency on one track can also bring up the off-axis sounds of adjacent mics, potentially creating more problems than it solves.

For a dull sounding kick drum, adding a slight boost anywhere around 80 Hz to 120 Hz will produce more boom and a more rounded “thud.” (Typically, the kick tends to compete with the bass guitar for that frequency range, and it’s a good idea to decide which of the two should occupy the lower and upper edges of that zone. See the section on bass later in this article for more on this.)

Adding a tiny bit of 500 Hz can bring out the “click” of the beater hitting the drum head, and can be helpful in preventing the kick from disappearing once your track hits the listener’s earbuds in the inevitable low-fi MP3 version.