How does equalisation shape the tone of a sound and help instruments sit together in a mix?
Equalisation: the frequency bands, high-pass and low-pass filters, shelving and parametric EQ, cut and boost, the Q (bandwidth) control, and using subtractive EQ to create space and corrective and creative EQ in a mix.
A focused answer to the Edexcel 9MT0 EQ content, covering the frequency bands, high-pass and low-pass filters, shelving and parametric EQ, cut and boost, the Q control, and subtractive, corrective and creative equalisation in a mix.
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What this dot point is asking
Edexcel wants you to use equalisation precisely: to know the frequency regions, the filter and band types, the cut and boost directions, and the Q control, and to apply EQ both correctively (fixing problems) and creatively (shaping tone and carving space). EQ is one of the most heavily examined production techniques in Component 4, where you must justify specific moves by frequency and type.
The answer
The frequency bands
Knowing where qualities live lets you reach for the right frequency directly. "Add presence" means lift the upper mids; "remove mud" means cut the low mids.
Filters: high-pass and low-pass
A high-pass on every non-bass track is a standard tidying move, clearing the low end for the kick and bass and reducing build-up.
Shelving and parametric EQ
Cut, boost and the Q control
Subtractive EQ (cutting) often sounds more natural than boosting and avoids piling up energy and raising the overall level. Carving a small dip in one instrument where another needs room (complementary EQ) lets both be heard.
Examples in context
When you high-pass a hi-hat at Hz, you remove low-end spill so it does not clutter the kick and bass. When a mix sounds muddy, a cut in the low mids of several tracks usually clears it. When a vocal lacks clarity against a busy band, a small presence boost plus a complementary cut on the guitars opens a slot for it. EQ is how you make room in the spectrum so every part can be heard.
Try this
Q1. What does a high-pass filter do? [1 mark]
- Cue. It passes frequencies above its cut-off and removes those below.
Q2. What does the Q control set on a parametric band? [2 marks]
- Cue. The bandwidth: high Q is narrow, low Q is wide.
Q3. Why is subtractive EQ (cutting) often preferred to boosting? [2 marks]
- Cue. It creates space and sounds natural without piling up energy or raising the overall level.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 9MT0/04 20194 marksA vocal recording has unwanted low-frequency rumble and a boxy build-up around Hz. Describe the EQ moves you would make to fix each problem, naming the type of EQ used and whether you cut or boost.Show worked answer →
For the low-frequency rumble, apply a high-pass filter (low-cut), setting the cut-off frequency around to Hz so that the rumble below the voice is removed while the vocal body is kept. This is a filter, not a boost or cut band, and it removes everything below its cut-off.
For the boxy build-up around Hz, use a parametric EQ band: set the frequency to about Hz, choose a moderately narrow Q, and apply a cut (reduce the gain) to remove the boxiness. Because the problem is a build-up, the move is subtractive (a cut), and a parametric band lets you target the exact frequency and width.
Markers reward a high-pass filter for the rumble (with a sensible cut-off), and a parametric cut at about Hz with a suitable Q for the boxiness, with the cut/boost direction correct for each.
Edexcel 9MT0/04 20224 marksExplain the difference between a shelving EQ and a parametric (bell) EQ, and explain what the Q control does on a parametric band.Show worked answer →
A shelving EQ boosts or cuts all frequencies above (high shelf) or below (low shelf) a chosen turnover frequency by a set amount, so it lifts or reduces a whole region of the spectrum, like a treble or bass control. A parametric (bell) EQ affects a band centred on a chosen frequency, tapering off on either side, so it targets a specific region rather than everything beyond a point.
The Q control sets the bandwidth of a parametric band: a high Q gives a narrow band that affects a small range of frequencies (good for surgical cuts of a single problem frequency), while a low Q gives a wide band that affects a broad range (good for gentle, musical tonal shaping). Q therefore controls how focused or broad the cut or boost is.
Markers reward shelf = everything above/below a turnover; parametric = a band around a centre frequency; Q = bandwidth (high Q narrow, low Q wide).
Related dot points
- Dynamics processing: the compressor and its parameters (threshold, ratio, attack, release, knee, makeup gain), gain reduction, limiting, the noise gate and expander, and creative uses such as controlling peaks, adding punch and parallel compression.
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A focused answer to the Edexcel 9MT0 effects content, covering reverb and delay, modulation effects (chorus, flanger, phaser, tremolo, vibrato), distortion, send versus insert effects and the wet/dry balance.
- The mixing process: setting levels and the static balance, frequency balance and avoiding masking, the three dimensions of a mix (level, frequency, stereo), creating depth, bus routing and submixing, and the goal of a clear, balanced mixdown.
A focused answer to the Edexcel 9MT0 mixing content, covering setting levels and the static balance, frequency balance and masking, the three dimensions of a mix, creating depth, bus routing and the mixdown.
- The harmonic series and timbre: fundamental and harmonics, how the relative levels of harmonics shape tone, the waveform shapes of basic tones, the frequency spectrum and the phase relationships that create a sound's character.
A focused answer to the Edexcel 9MT0 harmonics content, covering the harmonic series, fundamental and harmonics, how relative harmonic levels shape timbre, the basic waveform shapes, the frequency spectrum and phase.
- Panning and the stereo field: the pan control and stereo placement, mono and stereo, building width and separation, the pan law, phase and mono compatibility, and conventions for placing instruments in the stereo image.
A focused answer to the Edexcel 9MT0 panning content, covering the pan control and stereo placement, mono versus stereo, width and separation, the pan law, phase and mono compatibility, and placement conventions.
Sources & how we know this
- Pearson Edexcel A-Level Music Technology (9MT0) specification — Pearson Edexcel (2017)