Worked example · Music · Year 9
DCF: Producing → Creating digital content
A secure Year 9 sheet. Part A has exact right answers, listed below, and they all come from the facts box on the worksheet — you can mark them without knowing any music. Show this after Part B is written, so pupils design before they copy.
| Waveform | 2nd | 3rd | 5th | Which harmonics? | The sound |
|---|---|---|---|---|---|
| Sine | 0 | 0 | 0 | None at all — just the fundamental. | Pure, smooth, slightly hollow. Like a tuning fork or someone whistling. Nothing to it but the note itself. |
| Triangle | 0 | 0.11 | 0.04 | Odd only, falling as 1 ÷ n² (1/9 and 1/25). | Soft and a bit hollow. Brighter than a sine but the upper harmonics are so quiet it still sounds gentle — good for bells and flutes. |
| Square | 0 | 0.33 | 0.20 | Odd only, falling as 1 ÷ n (1/3 and 1/5). | Hollow and buzzy. Same harmonics as the triangle, but they are much louder, so it sounds far harder. Clarinets and old games consoles. |
| Sawtooth | 0.50 | 0.33 | 0.20 | Every harmonic, odd and even, falling as 1 ÷ n. | Brightest and buzziest of the four. It has the square's odd harmonics plus the even ones, which is why it sounds fuller. Brass and big string pads. |
Darkest to brightest: sine, triangle, square, sawtooth. "Brighter" is not louder — all four can play at the same volume and the same pitch. It means more of the sound's energy is sitting in the upper harmonics. The sine has none, the triangle's die away as 1 ÷ n² so they are nearly gone by the 5th, the square's only die as 1 ÷ n, and the sawtooth has the square's odd harmonics and all the even ones as well.
Evidences criterion 1: the numbers are right, the zeros are written in rather than dashed, and the brightness order is explained by which harmonics are present rather than by how loud the sound feels.
This is the envelope of Patch 3, the slow pad. Notice that the sustain section is flat and has no length of its own — it lasts exactly as long as the key is held, because sustain is a level, not a time. The release only begins where the red line is.
Criterion 3: the diagram makes the sustain-is-a-level point visually, which is the single thing pupils get wrong about ADSR.
| Setting | Patch 1 — sub bass | Patch 2 — bell pluck | Patch 3 — slow pad |
|---|---|---|---|
| Waveform, and why | Sine. It has no harmonics at all, so it fills the bottom without putting anything in the middle of the mix where the vocal is. | Triangle. Odd harmonics that die away as 1 ÷ n², so it rings like a bell instead of buzzing like a square. | Two sawtooths, detuned slightly. Every harmonic is there, which gives the filter plenty to work with, and the detuning makes it wide. |
| Filter cutoff | 200 Hz. Honestly this barely does anything — a sine has no upper harmonics to remove. It is there as a safety net in case I swap the wave later. | 4000 Hz. High enough to keep the ring, low enough to shave off the hard edge of the attack. | 1200 Hz. Removes the top harmonics of the saws so the chords sit behind the melody instead of fighting it. |
| Resonance | Low. Any peak at the cutoff would make the bass boom on one note. | Low to medium. | Medium, so a slow cutoff sweep across the 16 bars can be heard. |
| Attack | 5 ms | 2 ms | 800 ms |
| Decay | 100 ms | 350 ms | 400 ms |
| Sustain | 90% | 0% — so the note dies after the decay even if I keep holding the key. That is what makes it a pluck. | 70% |
| Release | 120 ms. Short, or the bass notes smear into each other. | 250 ms | 2 s |
| Effect | None. Reverb on a sub bass just makes it muddy. | Delay set to a quarter note, plus a small room reverb. | Long hall reverb and a slow chorus. |
| Where it sits | Under the kick, one note per bar, in mono. | The melody, above the pad, entering at bar 7. | Holding the chords right through, quietest element. |
Criteria 2, 3 and 4: every box has a number, the sustain of 0% on the pluck is explained as a level, the cutoff choices are justified by what they remove, and the note about the sub bass filter doing almost nothing shows real understanding rather than filling boxes in.
| Test | What I heard |
|---|---|
| Sine, then sawtooth, same note | Same pitch, completely different character. The saw was buzzy and seemed much louder even though the meter barely moved, because all those extra harmonics are in the range my ears are most sensitive to. The sine nearly disappeared on the laptop speakers and only came back on headphones. |
| Low-pass sweep from the top down to 400 Hz | The brightness peeled off the top downwards, like the sound was being moved behind a closed door. By 400 Hz I could only hear the fundamental and a hint of the next harmonic or two. |
| The same sweep with resonance up | A whistle appeared and slid down with the cutoff, because resonance boosts a narrow band right at the cutoff point. Turned up further it almost started singing a note of its own. |
| Attack 1.5 s, then 2 ms | At 1.5 s the note faded in and was useless for anything rhythmic — by the time it was loud, the beat had moved on. At 2 ms it was instant and slightly clicky on the front. |
| Sustain 0%, key held down | The note rose, fell to silence and stayed silent while my finger was still on the key. That proved sustain is a level and not a length of time. |
| Which patch missed my prediction? | The pad. At 1200 Hz with medium resonance it whistled every time I changed chord, which I had not expected. I dropped the resonance to low and lifted the cutoff to 1600 Hz, and it sat behind the melody properly. |
Criterion 5: it reports what happened rather than what should have happened, and the last row names the change made and the reason for it.