EQ, short for equalization, raises or lowers the level of chosen frequency ranges. It lets you turn the low, middle and high parts of a sound up or down on their own, without touching the rest. You use it to clean out what a part does not need, to make room when two sounds clash, and to gently shape tone.
The controls are the same on almost every EQ, hardware or plugin: a set of bands, each with a shape, a frequency and an amount, read against a display of the spectrum. The frequency figures here are approximate zones, not exact rules, and every sound is a little different.
An EQ raises or lowers the level of chosen frequency ranges, so you can shape the balance of a sound's lows, mids and highs without changing anything else. Turn a range down and that part of the sound gets quieter; turn it up and it gets louder. Everything you leave alone passes through untouched.
This works because almost no sound is a single pitch. A note carries a fundamental plus a stack of harmonics above it, and layered on top is noise, room tone and rumble. All of that spreads across the frequency range at the same time. An EQ splits that range into bands you can adjust one by one, so you can pull down a boxy resonance low down while leaving the brightness up top exactly as it was.
A cut reduces the energy in a range and a boost adds to it. Most EQ work is a mix of the two: small cuts to remove what is in the way, small boosts to bring out what you want more of. Because you are only moving levels, an EQ does not add anything that was not already in the sound. It can only turn up or turn down what is there.
There are two jobs an EQ does, and it helps to know which one you are doing. Corrective EQ fixes a problem: rolling off rumble, taming a harsh resonance, cutting one part back so another can be heard. It is usually narrow and precise. Tonal EQ shapes character: a gentle, wide lift to add warmth or air, to make a sound feel a certain way. It is usually broad and subtle. Same tool, different intent.
Each band is a filter with a shape, and the shape decides which part of the spectrum it acts on and how. Most EQs give you the same handful. Here is what each one does and when you reach for it.
| Band type | What it does | Common use |
|---|---|---|
| High-pass (low-cut) | Removes everything below a frequency you set and lets the higher content pass. The lower you place it, the less it takes. | Clearing rumble and unused low end off anything that is not the bass |
| Low shelf | Raises or lowers everything below a set point by the same amount, like a gentle ramp rather than a cliff. | Adding or trimming overall weight and warmth |
| Bell (peak) | Boosts or cuts a hump centred on one frequency, with the width set by the Q control. The everyday workhorse. | Cutting a resonance or lifting a specific range |
| High shelf | Raises or lowers everything above a set point by the same amount. | Adding air and brightness, or taming it |
| Low-pass (high-cut) | Removes everything above a frequency you set and lets the lower content pass. | Softening hiss or harshness, pushing a part back |
| Notch | A very narrow, deep cut aimed at a single frequency. | Removing hum, a ringing resonance or feedback |
The bell is the one you will use most, and it has three controls worth understanding. Frequency sets where the band is centred, so which part of the sound you are acting on. Gain sets how much you boost or cut it, in dB. Q, or width, sets how wide a range around the centre the band affects: a high Q is narrow and surgical, good for cutting a single problem spot, while a low Q is wide and gentle, better for shaping tone across a broad range.
A high-pass and a low-pass are not special effects, they are cuts with a fixed shape. A high-pass is a permanent cut of everything under its frequency, a low-pass a cut of everything over it. Because they clear whole regions a part never needed, they often do more for a mix than any boost, and they are usually the first bands to set.
When in doubt, cut. Removing what is wrong, called subtractive EQ, tends to sound more natural than boosting what is missing, called additive EQ, so a good habit is to cut before you boost. Both have a place, but reaching for a cut first keeps you out of trouble.
Cutting works well because most problems are things you want less of: a boxy resonance, a build-up of low mids, a harsh spike. A narrow cut removes the offending spot and leaves the rest alone, and because you are lowering level rather than raising it, you are not also pushing up noise or edge that was sitting nearby. To find the spot, some people boost a narrow bell hard, sweep it across the range until the ugly frequency jumps out, then pull that same band down into a cut.
Boosting has its place too, mostly for tone rather than repair. A gentle, wide boost, a couple of dB with a low Q, can add warmth low down or air up top in a way that sounds musical because it lifts a whole region rather than a single point. The rule of thumb that follows from this is cut narrow, boost wide: precise cuts to fix, broad lifts to flatter.
A boost raises the level of a part, and a slightly louder sound almost always seems better in a quick A/B, whether or not the EQ actually helped. Before you keep a boost, match the loudness of the changed version to the original and switch between them. Often the move that seemed like an improvement was just a jump in volume.
Start by high-passing everything that is not the bass to clear the low end, then find the two parts that clash and carve a dip in the less important one right where the other needs to sit. Making that kind of room, called unmasking, is what EQ does best once a mix gets crowded.
The problem in a busy mix is masking: when two sounds share the same range, the louder one hides the quieter one and your ear cannot separate them. A vocal and a rhythm guitar both crowding the mids is the classic case. The fix is a small cut in the part that matters less, placed at the frequency the important part lives in, so the two stop fighting over the same space. That is complementary, or carving, EQ, and it clears clutter that no amount of volume riding will.
It helps to know roughly where each thing lives, so you carve with intent instead of guessing. This map is approximate and the ranges overlap, but it is a reliable place to start.
| Range | What lives there | What EQ does there |
|---|---|---|
| Sub, ~20 to 60 Hz | Felt more than heard. Kick and bass fundamentals. | High-pass it off everything that does not need it, so one part owns the bottom. |
| Low, ~60 to 200 Hz | Weight and punch. Bass, kick body, low notes of guitars and keys. | Trim where too many parts pile up, so the bottom stays solid, not woolly. |
| Low mids, ~200 to 500 Hz | Body and warmth. Guitars, piano, snare, the chest of a vocal. | The usual place to carve, since this is where sounds turn boxy and muddy. |
| Mids, ~500 Hz to 2 kHz | Presence and definition. Where most instruments and the vowel of a voice sit. | Make room here between clashing parts; cut gently rather than boost. |
| High mids, ~2 to 6 kHz | Attack and intelligibility. Consonants, pick, the snap of a snare. | A small lift adds clarity; too much turns harsh, so go easy. |
| Highs, ~6 to 20 kHz | Air and sparkle. Cymbals, breath, shimmer. | A gentle high shelf opens a sound up; a low-pass softens hiss. |
If it is not two parts clashing but the whole mix sounding thick and cloudy at once, that is usually mud, a build-up in the low mids, and it has its own order of moves. We wrote a separate guide on clearing it: why does my mix sound muddy.
The cleanest fix for two sounds fighting is often not EQ at all. If you can change one part so it stops sharing the range, by moving its pitch, changing the voicing, or simply not playing both at once, you solve the clash at the source and never need the cut. EQ is powerful, but reach for the writing first when you can.
Half of a clean mix is decided before you open an EQ. A sound that is focused and already sits in its own part of the range needs far less corrective work than one that spills low end everywhere and fights its neighbours. The less you have to fix, the more EQ becomes a tool for tone rather than damage control.
We do not sell an EQ plugin, and this page is tool-agnostic on purpose. But where EQ starts is the source sound, and that is what we make. The Collection is our three instruments together, ARGISH, SILT and REHEAT, with three separate licence keys. They make clean, focused sounds that already sit in their own part of the range, so they stack without crowding and you reach for corrective EQ far less. ARGISH is a self-playing drone synth, SILT is a tape-loop instrument, and REHEAT writes acid lines. Every one ships as an Audio Unit, a VST3, an AAX for Pro Tools and a standalone app on macOS, and as a VST3 on Windows, all signed and notarized.
You can hear one free in your browser first, no install and no account, then decide.
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