Equalization (EQ)

Make no mistake: Equalization (EQ) is probably the most important skill to learn as a mixer, engineer, and music producer. Whatever else you want to do to your music is optional; EQ is necessary. Let's begin.

We'll start by turning back the hands of time to nearly 100 years ago, when two people named Harvey Fletcher and Wilden Munson were studying why we tend to have a hard time hearing really high frequencies and really low frequencies when those frequencies had the same amplitude as mid-range frequencies. They conducted some experiments on human subjects, asking a bunch of people to indicate the "loudness" of sounds at different frequencies. "What did they find," you ask? Exhibit A (from Wikipedia):

Don't worry too much about the units and numbers: what is important here is that these red curves are decreasing until about 3KHz, and then increasing after that. In other words, we hear music better between ~100-4000Hz than we do for sounds outside that range. All along our eardrum, we have hair-like receptors that convert soundwaves into information to send to our brain; the closer to the base of the drum the receptors are, the lower the frequency they're responsible for. And you guessed it: most of these hair-like receptors are in the middle of our eardrum. (If you're curious why this is the case, it's likely because our auditory system has adapted and evolved to better hear human speech.)

What this means for us is that we have to be particularly careful in creating music that has too much energy (volume) in any of these frequencies, because the little hairs in our ears can only perceive so much information before they fatigue. (Also, our brains are lying to us.)

One more thing before moving on: you'll notice these curves are different at different dBs! This is why sometimes when you listen to something on low volume, you won't hear the bass as well. When you turn up the volume, the Fletcher-Munson curve flattens, and the bass is heard clearer in the mix! Pro-tip takeaway: try EQing on different volume levels, knowing that your bass and very high frequencies will poke through better when you're EQing on high volumes :)

Ok, so we know how precious sound is now and how we have to be parsimonious with the sounds we use to compose music. How does this help me be a better music producer?

If there's one rule I learned, it's that the ear don't lie! If something sounds too strong or too loud to you, it's because it is. We have different adjectives for loudnesses in different frequency ranges. I'll help you decode them:

Frequency Range 1: <100 Hz - Low Frequency Range

Good sounding description: Punchy

Bad sounding description: Boomy

Frequency Range 2: 100 Hz to 500 Hz - Low-Mid Frequency Range

Good sounding description: Warm

Bad sounding description: Muddy, Hooting

Frequency Range 3: 500 Hz to 1,000 Hz - Medium-Mid Frequency Range

Good sounding description: Full

Bad sounding description: Boxy (like it was recorded in bare room)

Frequency Range 4: 1,000 Hz to 10,000 Hz - High-Mid Frequency Range

Good sounding description: Clear

Bad sounding description: Harsh

Frequency Range 5: >10,000 Hz - High Frequency Range

Good sounding description: Crisp

Bad sounding description: Strident

Quick exercise: go through your sound of choice with an EQ and boost these frequencies one by one to confirm these descriptions. You'll be relying on these for the rest of your music production career, so if you disagree, come up with a new adjective to describe what you hear!

Let's take one last detour back to Fletcher and Munson: if you have hearing loss ("WHAT?!"), be aware that your mix may sound crisp to you, but strident to others in the music-listening world! Get an opinion from a friend, whether they are in music or a layperson, and ask them what they hear out of your sound!

Boosting is Addition, Cutting is Subtraction

Think like a sculptor for a moment. You're asked to make David from a slab of stone. Great. Now think of EQ the same way.

Generally, especially in mixing, you're going to want to cut before you boost. The idea here is that you are already adding dozens of tracks together, all of them fighting for your hair receptors' attention. A solo saxophone can be enough to make people cover their ears; you think you'll be able to combine the elements of a big band and not have to EQ??

Tracks build up over the five frequency ranges, and we need to cut the excess of sound to create something beautiful. Generally, you want