Celesta

The struck bar to scale (thickness ×4) on its two blocks, over its box, and its first three bending modes moving with their live amplitudes, slowed down. ▼ hammer, ▬ damper felt; the box fills with colour as it takes the bar’s energy.

The energy in the bar and in the air of its box over the last 3 s (60 dB tall). Close together they trade it back and forth, and the box radiates it: that is what makes a celesta note short and sweet.

A plain bar’s overtones at 2.76 and 5.40 × the pitch are not harmonics: they give the attack its bell-like glint, then die long before the fundamental.

The upper modes vanish within a fraction of a second and leave the fundamental, held up by its box; letting a key go drops the damper and cuts every line at once.