EQ is everywhere, from the bass and treble knobs on your stereo to the audio settings on streaming services. It’s a fundamental tool used by audio engineers to shape sound.
In this article, we’ll answer the question, what is EQ in music? We’ll break down the basics of EQ and show you how to use it to make your mixes sound clear and balanced. Let’s dive in!
Key takeaways
- What is EQ? EQ is the process of changing the volume, or “amplitude”, of specific frequencies in a sound
- How many frequency bands are there? There are seven main frequency bands: Sub (20Hz – 60Hz), Bass (60 – 250Hz), Low Midrange (250 – 500Hz), Midrange (500Hz – 2kHz), Upper Midrange (2 – 4kHz), Presence (4 – 6kHz), and Brilliance (6 – 20kHz)
- What are the different EQ parameters? Most modern EQ plugins and hardware will offer the following controls: Gain (volume), Bandwidth (Q-Factor), and Slope (Filter)
- What different EQ curves are there? The most common EQ curves are Bell filters, High and Low-pass filters, and High and Low Shelves
- What is the best way to use EQ? The number 1 top tip is to not EQ in solo; you should always check how your EQing affects the context of a mix to ensure you get the best sound from your processing
What is EQ in music?
Equalization (EQ) in music is the process of adjusting the volume, or “amplitude”, of specific frequencies or groups of frequencies in a sound.
A frequency refers to the rate at which sound waves oscillate, creating the sensations of pitch and tone our brains interpret as sound. These sound waves are vibrations in air pressure that travel to our ears, where they are converted into electrical signals and processed by our brain as sounds.
Music and sound are a blend of multiple sound waves vibrating at various frequencies simultaneously. These frequencies are measured in Hertz (Hz) or kilohertz (kHz), representing the number of cycles per second. The higher the frequency, the higher the pitch we perceive. For example, a sound wave at 20 Hz has a very low pitch, while one at 20,000 Hz (20 kHz) has a very high pitch.
EQ allows you to select specific frequency groups and adjust their amplitude by boosting (increasing) or cutting (decreasing) their volume. This is typically done using sliders or knobs, depending on the EQ style. By using EQ, you can fine-tune your music to ensure each element sits perfectly in the mix, creating a polished and professional sound.
Frequency spectrum
The frequency spectrum refers to the range between the lowest and highest frequencies that audio equipment can reproduce and is measured in Hertz (Hz) and kilohertz (kHz). It spans from 20Hz to 20kHz, covering the typical human hearing range and is often split into smaller “bands” to describe the frequency characteristics.
For a detailed explanation of the frequency bands and the frequency range they occupy, see the table below or our guide to audio frequency range.
| Sub-bass | 20 Hz – 60Hz | Felt more than it’s heard and takes high-quality headphones or speakers to reproduce; most instruments struggle to enter this range. |
| Bass | 60 – 250Hz | Determines the overall power of the music, largely emphasised by bass synths, bass guitars, bass drums, or piano. |
| Low midrange | 250 – 500Hz | Most acoustic instruments' fundamental frequencies are found here, defining the depth of the instrument. |
| Midrange | 500Hz – 2kHz | An important area where the bulk of most instruments lie, adding clarity and detail to stand out in a mix. |
| Upper midrange | 2 – 4kHz | The most sensitive area to human hearing, meaning vocal plosives and sibilance is prominent in this area. Too much build-up in this area can create listening fatigue. |
| Presence | 4 – 6kHz | Enhances the definition of sounds. Drum cymbals occupy this space extensively, whereas other instruments rely on overtones in the region to provide the definition. |
| Brilliance | 6 – 20kHz | Responsible for adding a “sheen” of air to the sound and helping lift the overall brightness. Softening this region creates a warmer and more distant sound. |
Timbres and fundamental frequencies
So far, we’ve discussed frequencies as if they are static, but the reality is more complex. Music is a combination of sound waves vibrating at various frequencies, and these frequencies determine a note’s pitch. However, each instrument’s unique construction contributes to its harmonic content, which creates its distinctive sound, aka, timbre.
If you pluck a string on a guitar and run it through a frequency analyser, you’ll see multiple frequencies, not just the fundamental note. This is because the sound is made up of sine wave components called “partials.” When partials are related to the fundamental frequency by whole number ratios (e.g., 2:1, 3:1), they are harmonic. In contrast, unrelated partials are inharmonic.
Two different instruments playing the same note will produce different timbres, even though they share the same fundamental frequency. For instance, a bowed cello string is rich in evenly related partials, creating a highly harmonic sound, while a cymbal crash consists of unrelated partials, making it highly inharmonic. These characteristics give each instrument and sound its unique timbre.
When to use EQ
EQ is the most important mixing plugin you’ll use in production. Essential for everything from subtle tweaks to dynamic effects, think of EQ as your go-to tool for repairing, adding clarity, balancing, and even mastering your tracks.
EQ can be a powerful tool for creating space in a mix by addressing frequency masking issues.
Frequency masking occurs when instruments with overlapping frequencies clash, causing muddiness and making it hard to distinguish between sounds. For example, if the kick drum and bass guitar are fighting for the same frequency range, EQ can help by cutting or boosting certain frequencies to clear space for each instrument, resulting in a cleaner, more defined mix.
A gold standard among EQ plugins for dealing with frequency masking is Sonnox Toolbox Claro, which offers multiple visualisers that let you stack the frequency curves of other instruments on top of each other to see where in the range they overlap, letting you dial in their EQ to sit perfectly in a mix.
EQ is also essential for fixing problematic frequencies and harsh resonances that stick out in a mix. For instance, a distorted electric guitar might sound fantastic in solo but in a mix, it has an unpleasant whistling and ringing frequency in the upper midrange that can be heard above all other instruments in a mix. Using a narrow EQ filter, you can surgically cut these frequencies for a cleaner mix.
Beyond just fixing problems, EQ is also a creative tool. You can transform a sound by drastically altering its frequency content. For example, applying a high-pass and low-pass filter to a vocal can create a ‘telephone’ effect, adding interest and variation to your mix.
If you want an extremely creative EQ, the Sonible Smart:EQ 4 should be on your radar. This EQ lets you upload or use preloaded custom EQ templates that the plugin will automatically match your signal with; get as creative as you want!
Different EQ modes and how to use them
Bell filters
Bell filters are the standard EQ shape that is distinguished by its bell-like shape. The shape of a bell filter is determined by the Q-factor parameter which is responsible for how broadly frequencies around the centre frequency will be affected when boosting or cutting.
Bell filters are used in most EQ types, from graphic EQs to parametric EQs, with varying degrees of flexibility. In graphic EQs, the Q-factor is pre-determined on each frequency band whereas with parametric EQs, you will have access to the Q parameter for more precision.
As the width of a bell filter can be adjusted on a parametric EQ, they’re incredibly useful for different applications in your mix. Setting a wide Q will allow you to make broad adjustments across a large frequency range, a typical EQ move when mastering.
Conversely, setting a very narrow bell filter is convenient for removing unwanted resonances or whistles with precise surgical cuts.
Practically an industry standard, the FabFilter Pro-Q 3 is the perfect EQ plugin to go for when looking to get started with shaping EQ curves using bell filters. Its simple interface makes placing bell filter EQ curves easy, and they can be completely customised with Q-factor and slopes for enhanced control.
High and low-pass filters
Named for the frequencies they leave in your signal, rather than what is removed, high and low-pass filters can also be named low-cut and high-cut filters respectively. These filters are used to remove entire frequency ranges beyond the threshold of the centre frequency you set.
A high-pass filter cuts all frequencies below a selected cutoff point, helping to eliminate unnecessary low-end sounds from instruments that don’t require them. For example, you can use a high-pass filter to remove frequencies below 90 Hz from a guitar, freeing up space for the bass guitar or kick drum.
A low-pass filter, on the other hand, cuts all frequencies above the cutoff point, useful for reducing piercing high-frequencies in cymbals or brass instruments. Both filters often include slope controls, which dictate the steepness, measured in dB/oct, of the cutoff, similar to the Q control on bell EQs.
High and low shelves
Shelf filters boost or cut frequencies above or below the threshold frequency, in a similar way to high and low-pass filters, but are less aggressive and with more control.
Applied from either the high or low-end frequencies, these are ideal for broad, subtle changes, much like a traditional “Bass” and “Treble” control on your Hi-Fi system.
Shelf filters are the go-to filter type for enhancing or subtly controlling the high-end sparkle and low-end thump of any sound in a mix, or the entire mix as a whole.
A low-shelf filter is often used to remove excessive low end in percussive instruments as it has a more natural effect on the phase response, allowing for the punchy transients to not get smeared. Additionally, you can use it to apply a general low-end lift, not centred around a specific frequency, for a more natural and rounded low-end.
A high-shelf filter can brighten a track by applying it in a subtle sweep from the high-midrange up, gradually getting steeper the higher into the frequency range it goes, making it ideal to add “air” to a lead vocal. It can also be used to subtly attenuate treble material more gently than a low-cut filter.
When looking to use a shelf EQ, you should use a Pultec-style EQ, such as the Apogee Bundle Pultec. These EQs are known for their incredibly smooth shelves in the high and low end, adding weight and brightness without any unwanted muddiness or harshness, making them ideal for any kind of instrument you’re EQ’ing
Transient EQ
Transient EQ allows for separate processing of the transient (initial impact) and sustained (body) portions of a sound.
This innovative approach means you can EQ these elements individually and recombine the signal at the output.
It offers precise control over the attack and body of a sound, allowing for unique sculpting and enhancement.
With transient EQ, you could boost high-end stick attack in the transient portion of a snare drum, whilst boosting the low and low-mid punch in the sustain portion completely independently for tremendous levels of control in tonal shaping.
There aren’t many options available for this type of EQ, but the undeniable king for transient EQ is the Eventide SplitEQ.
EQ controls explained
Slope
The slope of a filter sets the steepness at which filters like high-pass (HPF) and low-pass filters (LPF) attenuate sound beyond their threshold frequency. Measured in decibels per octave (dB/octave), the slope indicates how aggressively frequencies are reduced past this point.
Common slopes range from 6dB/octave to 24dB/octave, though advanced digital EQs can create slopes up to 96dB/octave. A lower slope, such as 6 or 12 dB/octave, produces a gentle, transparent roll-off, ideal for subtle adjustments. In contrast, higher slopes like 24 or 48 dB/octave provide sharper cut-offs, perfect for aggressive filtering at precise frequencies.
Modern EQs also allow slope adjustments for bell or shelving bands, enhancing flexibility in sound shaping.
Q (Quality Factor)
The Q, or Quality Factor, controls the bandwidth of an EQ band, determining how wide or narrow the boost or cut will be. Essentially, Q lets you adjust the range of frequencies the equalizer will affect. Higher Q values result in a narrower bandwidth, targeting specific frequencies, while lower Q values affect a broader range of frequencies.
For instance, Q values less than 1 create broader EQ curves, ideal for gentle tone shaping, whereas values greater than 1 offer tighter, more surgical boosts or cuts, making it particularly successful for removing unwanted, harsh and static resonances at a specific frequency. The Q control is crucial for fine-tuning the responsiveness of your EQ to make the effective changes you want in your sound.
Gain
Gain controls the amplitude of the selected frequencies, functioning as a volume knob for those frequencies. Measured in decibels (dB), gain adjustments determine the extent of the boost or cut applied with your EQ. Positive gain values indicate a boost, increasing the volume of the selected frequencies, while negative gain values mean a cut, reducing their volume.
By adjusting the gain, you can enhance or reduce specific elements in your mix, making certain frequencies more prominent or less obtrusive. This control is crucial for achieving a balanced and polished sound, allowing you to fine-tune the overall tonal balance of your music.
Our top tips for EQ’ing your mix
Tip 1: Remember, EQ alters volume
When you adjust EQ, you also affect the overall gain of your signal. This means that extreme EQ settings can significantly change your levels. It’s essential to keep gain staging in mind to avoid running out of headroom.
As you boost certain frequencies, the overall volume increases, potentially causing clipping or distortion. Conversely, cutting frequencies can lower your signal’s volume, which might necessitate compensation to maintain a balanced mix.
Always monitor your levels and make small adjustments to ensure your mix retains clarity and headroom without unwanted peaks.
Tip 2: Don’t overdo it
When EQing, especially in solo, it’s easy to overdo it, hunting for more problem areas to cut and pleasant frequencies to boost. Over-EQing can strip the character from the original recording, making it sound unnatural.
There’s no fixed rule for the amount of boost or cut or the number of bands to use, but it’s vital to maintain the core structure and frequency balance. Aim to preserve the original sound’s integrity, avoiding excessive tweaking that could lead to a flat, lifeless mix. Subtle adjustments often result in a more natural and pleasing sound.
Tip 3: Don’t rely on EQ’ing in solo
If you struggle to hear EQ changes with a 1dB or 2dB adjustment, try bringing that channel up in the mix rather than EQ’ing in solo. EQ’ing in solo can mislead you as it lacks the context of the full mix. Instruments need to sound good within the mix, not just on their own.
In solo, you might forget how the instrument interacts with other elements. No listener will hear the guitar in solo; they will hear the whole mix. Practising EQ with the mix playing helps you make better decisions that ensure each element fits cohesively.
Tip 4: Think about the full spectrum
When adjusting EQ, consider the full frequency spectrum rather than focusing on a single region. For example, if an electric guitar sounds boxy, you might instinctively cut the midrange. However, boosting the top-end and low-end can create the illusion of a cut midrange by enhancing other frequencies.
Similarly, if a sound seems dark, removing some low-end might brighten it without boosting the high-end. This holistic approach can yield more balanced and natural-sounding results, enhancing clarity and depth without overcompensating in one area.
Tip 5: Automate with the track
EQ typically applies static boosts or cuts, but instruments produce different frequencies and harmonics with each note. Songs may change key or playing style, meaning static EQ settings might not always yield the best sound.
Use automation to adjust centre frequencies, curve shapes, and Q-factor dynamically throughout the track. This ensures your EQ settings adapt to the changing elements of the song, providing a consistent and optimal sound across different sections.
- An extra bonus tip for you! If you’re not confident with automation and EQ yet, take a look at the Sound Radix SurferEQ. This EQ automatically adjusts the EQ curve based on the pitch of the input signal with real-time tracking.
EQ in mastering
In mastering, EQ is applied broadly and conservatively to balance the overall tonality of a track, ensuring consistency across an album or EP. The goal is to enhance a good mix for different playback systems, not to remix it.
Mastering EQ allows you to sculpt the master, remove frequency masking, and create space. Use broad, wide Q factors for boosting and tight surgical bands for cutting. Subtle changes up to 3dB in the midrange at 1kHz can add clarity, adding a subtle high-pass filter between 40-60Hz can clean unwanted rumble and shelving boosts above 8kHz can enhance brightness and articulation.
FAQs
What does EQ do?
EQ is the process of balancing frequencies in an audio signal. This involves adjusting the volume and Q parameter of specific frequency bands to shape the sound. By boosting or cutting certain frequencies, EQ helps achieve a more balanced sound or highlight particular elements within the audio.
Does EQ make music sound better?
EQ improves sound by fine-tuning the balance of frequencies within a track. By cutting unwanted frequencies and boosting others, EQ helps correct imperfections and ensures that all elements of the audio work well together. This process significantly enhances the clarity and quality of the music.
How do I EQ my audio?
To EQ your audio, set the centre frequency for the desired band, then set the type of EQ filter and adjust the gain control to boost or cut that frequency. The bandwidth or ‘Q’ control determines the range of adjacent frequencies affected, allowing precise control over the audio’s tonal balance.
Final thoughts
Now you’ve been provided with the tools to help sculpt your sound, you should understand how to EQ your mix. We’ve covered the frequency spectrum, key EQ parameters, and common uses in music production, and hopefully, we’ve provided the answer to, What is EQ in music?
Now, it’s time to apply what you’ve learned and create something amazing. Happy mixing!
Want to learn more, why not take a look at our other articles and continue learning?
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