Quiet but confident classroom voice: my thirteen-year-old picked up the violin this year and these two units turned curiosity into clear computation. Using a monochord and middle C = 261.63 Hz, they halved strings to reveal octaves, used the 2:3 ratio to find the perfect fifth (G), and methodically assembled a Pythagorean C scale with octave adjustments. Unit 1 developed proportional reasoning—translating ratios into frequencies—after one demonstration and then independent reconstruction. Unit 2 sharpened interval-ratio calculations: dividing frequencies, applying consistent rounding rules, converting terminating and repeating decimals back into simplified fractions (using basic algebraic conversion for repeating decimals), and recording exact ratio → decimal → simplified fraction for each degree. With light scaffolding they corrected minor rounding choices, showed tidy work, and gained procedural fluency. Progress aligns with Year 8 ACARA outcomes in proportional reasoning, operations with fractions/decimals, measurement, and The Arts (pitch and tuning). Result: exemplary accuracy, clear justification, and delighted engagement when a repeating decimal became a neat fraction. Next steps: focused ear training, hands-on tuning experiments, and comparisons with equal temperament to extend listening and mathematical insight. Send more strings.