CUORE

The thermistor's voltage as the heater fires, in the crystal's own time, as CUORE's digitiser would record it: each pulse rises as the heat reaches the thermistor's electrons and the wires charge, and fades as it leaves through the Teflon holders. The sound is this, sped up. The dashed line is what a pulse would be if the thermistor answered in proportion: where the solid one falls short, the crystal has warmed so far that it no longer does.

One crystal in its copper frame, held by Teflon clips, with the germanium thermistor and the heater glued to it, and the bias circuit out to the amplifier: each part glows as it warms above the heat sink. The thermistor's electrons sit above the crystal, warmed by the bias current.

Every key's pulses pass through the same filter, the bolometer's: its rise cuts the top and its fade the bottom, so the harmonics swell in one band whatever the note, like a voice's formant. Longer wires or a bigger crystal move it down; a warmer heat sink stretches the pulses' fall and lowers its bottom edge.