What is audio processing in SQA Higher Music Technology, and how do EQ and dynamics processors (compression, limiting, gating) shape a recorded sound?
Processing audio: using equalisation (EQ) to shape frequency content and dynamics processing (compression, limiting, gating, normalisation) to control level, and knowing what each does and why.
Audio processing in SQA Higher Music Technology: equalisation (EQ) to boost or cut frequency bands and shape tone, and dynamics processing (compression, limiting, gating, normalisation) to control the loud-quiet range, with the key controls (threshold, ratio, attack, release) explained.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
Processing is what you do to a captured sound to shape it: change its tone with EQ and control its loud-to-quiet range with dynamics processing. SQA Higher Music Technology expects you to understand the main processors, what they do, and the controls that drive them, so you can explain a processing choice and its effect. This dot point covers equalisation (high-pass, low-pass, shelving and parametric), and dynamics (compression, limiting, gating, normalisation), including the compressor controls (threshold, ratio, attack, release, make-up gain). A question asks you to name a processor and explain its effect on the sound.
The answer
Processing falls into two families. EQ (equalisation) changes the frequency balance of a sound by boosting or cutting bands: a high-pass filter removes low rumble, a low-pass filter removes high hiss, shelving lifts or drops everything above or below a frequency, and parametric EQ boosts or cuts a chosen band with a controllable width (Q). Dynamics processing changes the level relationship between loud and quiet: a compressor reduces the level of signal above a threshold (narrowing the dynamic range), a limiter is an extreme compressor that stops a signal exceeding a ceiling, a gate mutes signal below a threshold (removing noise between phrases), and normalisation raises the whole signal so its peak hits a target. Knowing what each does and why is the examinable skill.
EQ: shaping frequency
EQ adjusts how much energy a sound has in different frequency bands (roughly: lows give weight, mids give body and presence, highs give air and detail). The main filter and band types are:
- High-pass filter (low-cut): removes frequencies below a set point, clearing rumble, hum and mud (for example below 80 Hz on a vocal).
- Low-pass filter (high-cut): removes frequencies above a set point, taming hiss or harshness.
- Shelving EQ: boosts or cuts everything above (high shelf) or below (low shelf) a frequency, for broad tonal tilts.
- Parametric EQ: boosts or cuts a chosen centre frequency by a chosen amount, with a controllable Q (bandwidth) for surgical or broad changes.
EQ is used both correctively (removing a problem frequency, clearing space) and creatively (adding presence or warmth). Cutting is often cleaner than boosting because it removes problems without adding energy.
Dynamics: compression
A compressor reduces the level of any signal that rises above a set threshold, narrowing the gap between the loudest and quietest parts so a sound is more even and controlled. Its controls:
- Threshold: the level above which compression acts.
- Ratio: how hard the signal above the threshold is reduced (2:1 is gentle, 8:1 or more is heavy; infinity:1 is limiting).
- Attack: how quickly the compressor responds once the threshold is crossed (fast attack catches transients; slow attack lets them through).
- Release: how quickly it stops compressing as the signal falls back.
- Make-up gain: a level boost added after compression to bring the now-quieter signal back up.
The result is gain reduction on peaks and a steadier, more present sound, the reason vocals, bass and drums are routinely compressed.
Dynamics: limiting, gating and normalisation
- Limiter: a compressor with a very high ratio and fast attack that prevents the signal exceeding a set ceiling, used to maximise loudness without clipping (especially in mastering).
- Noise gate: mutes signal below a threshold, so quiet noise (hiss, hum, spill) between phrases is silenced while the wanted signal above the threshold passes; useful on noisy guitar amps or to tighten drums.
- Normalisation: a level change that raises (or lowers) the whole region uniformly so its loudest peak reaches a target level. It changes overall level only, not the dynamic range or tone (unlike compression).
Examples in context
Mixing a recorded vocal for the assignment, you might high-pass at 90 Hz to remove rumble, dip a boxy frequency around 400 Hz, lift presence around 4 kHz for clarity, then compress with a 3:1 ratio and moderate attack and release to even out the loud and quiet words, adding make-up gain to restore the level. The vocal now sits clearly and steadily in the mix.
On a noisy electric-guitar track, you might gate the signal so the amp hiss between riffs is silenced, EQ out harshness with a low shelf cut in the highs, and compress lightly for evenness. Each move is a named processor with a stated effect, which is precisely what the question paper rewards.
Try this
Q1. What does a high-pass filter do, and give a typical use. [2 marks]
- What the marker wants. It removes frequencies below a set point; a typical use is cutting low rumble and mud below about 80 Hz on a vocal so it is cleaner.
Q2. What does a noise gate do? [2 marks]
- What the marker wants. It mutes signal that falls below a set threshold, silencing quiet noise (hiss, spill) between phrases while letting the wanted signal above the threshold pass.
Q3. How does normalisation differ from compression? [2 marks]
- What the marker wants. Normalisation raises the whole signal uniformly so its peak hits a target level, changing overall level only; compression reduces the loudest parts, changing the dynamic range.
A note on sources
This guide is AI-written and not individually human-reviewed. The processing skills follow SQA's Higher Music Technology course specification (C851 76); verify current detail against the SQA Higher Music Technology documents at sqa.org.uk.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Higher specimen4 marksExplain how you would use EQ and compression on a recorded vocal, and the effect of each. (4 marks)Show worked answer →
A processing question. Two marks for the use and effect of EQ, two for compression, so treat them separately and explain effect.
For EQ: cut low frequencies below about 80 to 100 Hz with a high-pass filter to remove rumble and mud, and add a gentle boost in the presence range (around 3 to 5 kHz) to bring out clarity and intelligibility, so the vocal sits clearly in the mix. For compression: set a threshold so the loudest words are caught, a moderate ratio (for example 3:1), and suitable attack and release, so the difference between the loudest and quietest words is reduced and the vocal stays at a steady, present level throughout.
The discriminator is explaining the effect (clarity from EQ, evenness and control from compression), not just naming the processors. A weak answer says "use EQ to make it sound better" with no frequencies or controls.
Higher 20183 marksDescribe the controls threshold and ratio on a compressor, and what they do. (3 marks)Show worked answer →
A compressor-controls question. Marks reward a correct description of each control and the idea of gain reduction.
Threshold is the level above which the compressor acts: signal below the threshold is untouched, and signal above it is reduced. Ratio sets how much the signal above the threshold is reduced: a 2:1 ratio means that for every 2 dB the input goes over the threshold, the output rises by only 1 dB; a higher ratio (for example 8:1) clamps the level harder. Together they control how much the dynamic range is reduced.
A weak answer confuses threshold (where it starts) with ratio (how hard it squeezes), or omits the gain-reduction idea. The point is that a compressor reduces the level of the loudest parts so the overall dynamic range is narrower.
Related dot points
- Developing audio capture skills: choosing and positioning microphones, setting input levels and gain, and recording sources cleanly without distortion or noise.
Audio capture in SQA Higher Music Technology: choosing microphone types (dynamic, condenser, ribbon), reading polar patterns, positioning mics, setting gain to avoid clipping and noise, and recording sources cleanly for later processing and mixing.
- Understanding the audio signal path and hardware: how sound travels from source through microphones, cables, preamps, audio interfaces and mixing desks to the recording, and how monitoring works.
The audio signal path in SQA Higher Music Technology: how sound travels from source through microphones, cables and connectors, preamps and audio interfaces, mixing desk channel strips, to the recording and monitors, including analogue-to-digital conversion.
- Using hardware and software to manipulate audio: editing in a DAW (cutting, copying, comping, fades, crossfades), and correcting timing and pitch (quantise, pitch correction, time-stretching), with sample rate and bit depth.
Editing and manipulating audio in SQA Higher Music Technology: DAW editing (cut, copy, comp, fades, crossfades), timing and pitch correction (quantise, pitch correction, time-stretching), looping, and the meaning of sample rate and bit depth for audio quality.
- Applying effects: using time-based effects (reverb, delay, echo) and modulation effects (chorus, flanger, phaser, tremolo) and distortion, and knowing what each does and how it is controlled.
Applying effects in SQA Higher Music Technology: time-based effects (reverb, delay, echo) that add space and repeats, modulation effects (chorus, flanger, phaser, tremolo) that add movement, and distortion, with how each is controlled and used on a recorded sound.
- Mixing and sequencing: balancing levels and panning, using MIDI sequencing and virtual instruments, automation, and producing a stereo mixdown, plus an awareness of mastering.
Mixing and sequencing in SQA Higher Music Technology: balancing levels and panning across the stereo field, MIDI sequencing and virtual instruments, automation of parameters over time, the stereo mixdown (bounce), and an awareness of mastering.
Sources & how we know this
- Higher Music Technology Course Specification (C851 76) — SQA (2024)
- Music Technology subject page (Higher) — SQA (2026)