Bar C4 under the glass
The iron bar from the side, tied on cork at the nodes of its lowest mode, bending in slow motion (hugely exaggerated). Its key lifts it against the turning cylinder; the cloth on its rubbed point (a riveted post below E4, the bent-up back end above) turns green while it sticks to the glass.
Under the cloth
Slip speed of the glass under the cloth over the last 21 ms. Flat on zero = stuck: once the bar sings, the cloth is carried along with the glass and snaps back once a cycle.
Spectrum
live output · markers: the bar's bending modesSpectrogram
live output · ticks: the spectrum's markersA bar speaks within a tenth of a second or so and holds its note while the key is down. The friction's stick and slip make true harmonics of the note; the bar's own overtones (2.76, 5.40 × the note) stay quiet because the cloth is set to drive only the lowest mode.