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date: 14 November 2019


  • Hugh Davies


Photoelectric keyboard instrument resembling an electronic organ, developed in France by the engineer Pierre Toulon with Krugg Bass between about 1927 (when a prototype was demonstrated) and 1934. Support was provided by several companies, including Pleyel. The instrument had two eight-octave manuals and a pedalboard. The sounds were generated by discs in which a ring of equidistant narrow slits were cut (54 slits were needed for the lowest note); behind them was a mask the profile of which determined timbre—a differently shaped mask was used for each timbre. The discs rotated in the path of a beam of light, which flashed through the slits, was shaped by the mask, and fell on a photoelectric cell (the instrument takes its name from the French ‘cellule photoélectrique’). One disc was used for all the notes in each octave; notes whose frequencies could not be produced by an integral number of slits in the disc were, perforce, out of tune, in some cases by as much as 1.5%. But the system of creating all the notes of an octave from one disc offered the unusual possibility of giving each octave a different timbre. In the mid-1930s Toulon proposed the related technique of synthesising speech from fragments of optical film soundtrack mounted on a drum....

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