Geigensatz

A keyboard of eighty-eight bowed strings, every bow on one crank.

Fig. 1. Front elevation, 1 : 11, the front rail removed. Below, the keyboard in plan, 1 : 5.
Fig. 2. Section through the rack, 1 : 8, from the bass end.
Fig. 3. Bow force against bow velocity, after Schelleng. A dot for each sounding string.
  1. A the crank
  2. B connecting rod
  3. C the rack
  4. D a bow
  5. E a string
  6. F the bridge
  7. G a key

Keys · MIDI after the motor starts

To play. Any MIDI keyboard; aftertouch, channel pressure or the mod wheel bears down, and the sustain pedal keeps bows on their strings. Or the computer keyboard, laid out as two rows of a piano from Z and from Q, with the arrow keys to change octave and Shift to bear down. Or the drawn keys: press nearer the front of a key to bear down harder, and strike fast for a hard attack. With no key down, all you hear is the machine.

What you hear. Every string is a model of a bowed string, and every bow is on one rack. A crank drives the rack back and forth, so twice a turn the rack stops and every bow on it changes direction. At that instant bow speed passes through zero, where no bow force is playable (Fig. 3), and each sounding string loses its Helmholtz motion and finds it again the other way. Bear down harder and the change grows rougher. Slow the crank and it comes less often.

The second rank. Draw it, and a second string and bow for every note stand behind the crank on a rack of their own. An arm on the same shaft drives that rack, set a quarter turn round from the first crank, as a locomotive’s two cranks are, so one rack is at full speed whenever the other is turning around. Every string still changes bow, but never all of them at once. Offset sets the angle: at 0 the racks move together and the second rank only doubles the first, and at 180 they move against each other but still reverse at the same instant. The second rack joins at the end of its stroke, where it waits, so drawing the stop can take up to a full turn of the crank.

Before it. Leonardo sketched a keyboard of bowed strings, the viola organista, in the Codex Atlanticus around 1488–89. Hans Haiden of Nuremberg built one around 1575, his Geigenwerck, and Praetorius described it in Syntagma Musicum (1619) and pictured it in a woodcut, Plate III of his Theatrum Instrumentorum (1620). Sławomir Zubrzycki built a working viola organista in 2013. All of them bow with wheels or belts, which never have to turn around. This one bows with a rack, which does, and every string changes bow at once.

Sound: digital waveguides after J. O. Smith and the Synthesis ToolKit, in an AudioWorklet. Drawing: cut in the browser as a line engraving, then colored by hand, or near enough. No libraries. More curios.