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date: 15 September 2019

Electronelocked

  • Hugh Davies

Extract

Electronic organ, several models of which were designed by Leslie (E.A.) Bourn from the early 1930s and manufactured by the John Compton Organ Co. (later Compton Organs Ltd) between the mid-1930s and 1970. In 1926 Bourn approached John Haywood Compton with a proposal for the production of a ‘pipeless’ organ, and was invited to join the staff of Compton’s company. By about 1928 Bourn had abandoned his original electromagnetic tone-wheel system of sound generation and had developed his pioneering electrostatic system. It is based on 12 identical electrostatic tone-wheels, which are rotated at different speeds, by means of a synchronous motor and a set of pulleys, to produce all the semitone intervals in an octave. Each tone-wheel mechanism consists of two discs. A Bakelite stator disc, 12.7 cm (5”) in diameter, has engraved on it a set of concentric sinusoidal waveforms, corresponding to a fundamental pitch and its octaves; these grooves are filled with a metallic conductive material. A rotor disc, containing appropriately positioned electrodes, is rotated at about 1 mm distance from the stator. When an electrical potential is applied to one or more of the waveform rings, a corresponding voltage is induced in the electrodes, the mechanism forming the equivalent of the two plates of a capacitor. Gliding sounds can be produced by a relay that briefly slows down the motor, it can be activated only when all the keys are released....

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