What is MIDI, how does it differ from audio, and how is a convincing sequenced part programmed?
MIDI and sequencing: MIDI as performance data not audio, note, velocity and controller messages, real-time and step input, quantisation and groove, programming drums and instruments with velocity and timing for a realistic result.
A focused answer to the Edexcel 9MT0 MIDI content, covering MIDI as performance data versus audio, note, velocity and controller messages, real-time and step input, quantisation and groove, and programming realistic parts.
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What this dot point is asking
Edexcel wants you to understand MIDI as performance data (not audio) and to program convincing sequenced parts. You must know the message types (note, velocity, controllers), real-time and step input, quantisation and groove, and how to use velocity and timing so a part sounds human rather than mechanical. MIDI sequencing is core to Component 2 and the Component 4 practical, which supplies a MIDI part to be realised.
The answer
MIDI versus audio
Because MIDI is data, it is fully editable after the event: you can move or change notes, correct timing, adjust velocities, transpose, change tempo without affecting pitch, and swap the instrument entirely. MIDI files are also tiny because they contain no sound.
MIDI messages
Real-time and step input
Quantisation, groove and realism
Examples in context
When a programmed drum part grooves convincingly, varied velocities and a loosened timing feel are behind it. When you change a synth bassline's instrument without replaying a note, you are exploiting that MIDI is editable data. When the supplied MIDI part in Component 4 needs realising, your programming, the velocities, timing and chosen instrument, determines how musical it sounds. MIDI sequencing is the craft of making data perform like a musician.
Try this
Q1. State the difference between MIDI and audio data. [2 marks]
- Cue. MIDI is performance/control data that triggers a sound; audio is the recorded waveform.
Q2. What does velocity control in a MIDI note? [1 mark]
- Cue. How hard the note is played, affecting loudness and often tone.
Q3. Why can full quantisation be a problem? [2 marks]
- Cue. It snaps every note exactly to the grid, sounding mechanical and removing human feel.
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 marksExplain the difference between MIDI data and audio data, and state two advantages of recording a part as MIDI rather than audio.Show worked answer →
MIDI data is performance information, not sound: it records messages such as which note is played, when it starts and stops, how hard it is played (velocity) and controller movements. The actual sound is produced when this data triggers an instrument (a synth or sampler). Audio data is a recording of the sound itself, a waveform captured by sampling.
Two advantages of MIDI: first, it is fully editable after recording, so you can change individual notes, correct timing (quantise), alter velocities, and even change the instrument or sound entirely without re-recording. Second, MIDI files are very small compared with audio and contain no sound of their own, and the same part can drive different instruments. (Other valid advantages include easy transposition and tempo changes without affecting pitch.)
Markers reward MIDI = performance/control data that triggers a sound, audio = the recorded waveform, and two genuine advantages (editability, small size, change of instrument, transposition/tempo independence).
Edexcel 9MT0/04 20225 marksA sequenced drum part sounds mechanical and lifeless. Explain how you would use velocity, timing and quantisation to make it sound more realistic.Show worked answer →
The mechanical sound comes from every hit being identical in level and perfectly on the grid, which a human drummer never produces. To add realism, vary the velocity of the hits: accent the backbeat, play ghost notes quietly, and give the hi-hats slight velocity variation so the part breathes dynamically (velocity affects loudness and often tone). Adjust the timing so the part is not perfectly rigid: a real drummer plays slightly ahead of or behind the beat, so either play the part in by hand or apply less than full quantisation. Use quantisation carefully: rather than snapping every note hard to the grid (which removes all feel), apply partial quantisation (a lower strength) or a groove/swing template, which tightens the timing while keeping some human variation.
Markers reward velocity variation for dynamics (accents, ghost notes), timing not perfectly rigid (ahead/behind the beat), and quantisation used partially or with a groove rather than fully, to keep feel.
Related dot points
- Subtractive synthesis: oscillators and waveforms, the voltage-controlled signal path (VCO, VCF, VCA), the filter and resonance, the ADSR envelope, the LFO and modulation, and how these combine to design a synth sound.
A focused answer to the Edexcel 9MT0 subtractive synthesis content, covering oscillators and waveforms, the VCO, VCF and VCA signal path, the filter and resonance, the ADSR envelope, the LFO and sound design.
- Sampling and sample-based synthesis: capturing and triggering samples, the sampler and key mapping, looping, time-stretching and pitch-shifting, slicing and reordering, warping to tempo, and creative sample manipulation.
A focused answer to the Edexcel 9MT0 sampling content, covering capturing and triggering samples, the sampler and key mapping, looping, time-stretching, pitch-shifting, slicing and reordering, and creative manipulation.
- Capturing and editing audio: setting levels and recording cleanly, non-destructive editing, cutting, trimming and moving regions, comping the best take, crossfades to avoid clicks, fades, and removing noises and breaths.
A focused answer to the Edexcel 9MT0 capture and editing content, covering recording cleanly, non-destructive editing, cutting and moving regions, comping, crossfades, fades, and removing noises.
- The digital revolution: the move from analogue to digital audio, the compact disc (1982), MIDI (1983), the digital sampler, hard-disk recording and the rise of the DAW, and software pitch correction such as Auto-Tune.
A focused answer to the Edexcel 9MT0 digital history, covering the move from analogue to digital, the compact disc (1982), MIDI (1983), the digital sampler, hard-disk recording, the DAW, and Auto-Tune.
- Timing correction: quantising MIDI and audio, the grid and note values, quantise strength and swing, groove templates, flexing or warping audio timing, and balancing tightness against natural feel.
A focused answer to the Edexcel 9MT0 timing-correction content, covering quantising MIDI and audio, the grid and note values, quantise strength and swing, groove templates, warping audio, and keeping a natural feel.
Sources & how we know this
- Pearson Edexcel A-Level Music Technology (9MT0) specification — Pearson Edexcel (2017)