Vibraphone

The struck bar to scale (thickness ×3) and its first three bending modes, moving with their live amplitudes, slowed down. The arch cut underneath is what puts them at 1 : 4 : 10. ○ cords at mode 1’s nodes, ▼ mallet, ▬ damper felt, ⌒ tube mouth.

Left: the tube under the struck bar, its air pressure in a quarter-wave standing wave (largest at the closed bottom), and the disc in its mouth turning with the shaft. Right: how the disc’s angle sets the coupling and the tube’s pitch over one turn (● now), and the energy in bar and tube over the last 4 s.

A tuned bar’s partials land on the harmonic grid at 4 and 10 × f₁ (two octaves, and three octaves and a major third); a plain bar’s at 2.76 and 5.40 do not.

The bar's upper partials die quickly and leave the fundamental ringing; with the motor on, the resonators' fans pulse every line.