What is EQ in audio?

By Dan Murtagh · Updated 27 September 2026

Short answer: EQ (equalisation) turns a range of frequencies up or down. It’s a volume control for part of the sound: the bass, the middle, the top, or a narrow slice of one of them. In mixing, you use it to make each instrument clearer and to help the instruments fit together.

This page is about EQ in mixing and recording. The EQ in a music app, a speaker or a pair of headphones works the same way, but on everything you play at once.

What EQ does

Every sound is many frequencies at once, from the low thud of a kick drum to the fizz of a cymbal. People hear from about 20 Hz, the lowest bass, to about 20 kHz, the very top. An equaliser changes the balance inside that range. Turn the lows down and a sound gets thinner. Turn the top down and it gets duller. Turn the middle down and it sounds hollow, as if it’s further away.

That’s the whole idea. Everything else about EQ is choosing which range, how much, and how wide.

The ranges, in plain words

These are the nine bands Mix Chops trains you to name, one octave apart. The words are the ones engineers use when they talk about too much or too little of each.

• 63 Hz, sub weight: felt more than heard. Kick weight, the lowest bass.
• 125 Hz, body and warmth: the note of the bass, the body of the kick, the chest of a voice.
• 250 Hz, the mud zone: almost every instrument has energy here, so it builds up.
• 500 Hz, boxiness: hollow, cardboard-box sounds, often from small rooms.
• 1 kHz, honk: nasal, like a voice down a phone line.
• 2 kHz, bite and attack: pick attack, snare crack, the part of a voice that cuts through.
• 4 kHz, presence and edge: consonants and the front of each note. Too much sounds harsh.
• 8 kHz, sizzle: cymbals, breath and S sounds.
• 16 kHz, air: openness above everything else.

Where each instrument sits across those bands is a chart of its own: see the EQ frequency chart on danmurtagh.com.

The controls

Most EQs in a DAW give you bands you can shape three ways. A bell lifts or dips a range around one frequency (parametric EQ explains frequency, gain and Q). A shelf lifts or lowers everything above or below a point (shelving EQ). A filter takes out everything below or above a point (high-pass and low-pass filters).

How to use EQ in a mix

1. Listen first, and name the problem. Too much of something or too little: muddy, boxy, harsh, thin, dull. Mix problems you can hear has a demo of each.
2. Find it. If you can’t tell where it is, set a boost, sweep it slowly across the range, and listen for the spot where the problem jumps out.
3. Fix it with the smallest move that works. Often that’s a cut. A vocal that won’t come through may need less of the same range in the guitars, not more in the vocal.
4. Flip it off and on at the same level. A boost sounds better partly because it’s louder. Match the levels before you decide.
5. Check it with the whole mix playing. A move that sounds right on a soloed track can be wrong in the mix, and the other way round.

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