HELMHOLTZ SOUND SYNTHESIZER BY MAX KOHL- THE EARLIEST ELECTRIC KEYBOARD, CA 1905

Wood, brass and steel sound synthesizer, signed "Max Kohl, Chemnitz, 1/8", 39½ x 29", mahogany base fitted with 11 steel tuning forks signed MK, each fork stamped with corresponding note and frequency in vs (vibrations per second, i.e. hertz). Forks 1-10 fixed between pairs of electromagnets and mounted vertically onto wooden platforms (numbered 1-10) along with brass Helmholtz resonators, each pair ranging in size according to their graduating frequencies, each platform with "Aus/Ein" [on/off] switch. 11th fork (marked UT2 256 vs) mounted horizontally onto wooden platform with electromagnetic coil mounted between tines, adjustable mercury cup below lower tine; one end of board fitted with 2 anodes and 2 cathodes for connection to external 20 volt power sources; other end of board fitted with keyboard of 10 keys (8 ivory, and 2 non-mammalian replacements), each corresponding to 1 tuning fork/resonator pair (UT2 256 vs; UT3 512 vs; SOL3 768 vs; UT4 1024 vs; MI4 1280 vs; SOL4 1536 vs; 1792 vs; UT5 2048 vs; RE5 2304 vs; &  MI5 2560 vs). All 11 platforms connected together in series with wire filaments from the horizontal tuning fork.

For a detailed description of how to operate this apparatus, and detailed references please go to www.sothebys.com 

Some oxidization to metal components including resonators, tuning forks, anodes/cathodes, electromagnets, and labelling plates; wear to edges of mahogany base; wear to keys, two keys replaced with modern, non-organic materials; mechanics of one key in need of repair; mercury-dipping pin formerly affixed to underside of main horizontal driving fork lacking, a small component which would have been mounted near the base of the horizontal tuning fork missing (possibly a secondary mercury cup); wiring appears to be intact. Mercury cup filled with non-toxic Gallium instead of Mercury; board has been tested and powered up using two 20 volt power sources (for a total of 40 volts) - individual forks were tested for continuity in wiring, but the continuity of wiring for entire board was not tested.
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A MAGNIFICENT EXAMPLE OF HERMANN VON HELMHOLTZ'S SOUND SYNTHESIZER, AN ELECTRONICALLY DRIVEN DEVICE USED FOR ARTIFICIALLY CREATING MUSICAL SOUNDS OF DIFFERENT TIMBRE, AND THE VOWELS OF THE HUMAN VOICE. The Helmholtz Sound or Vowel Synthesizer was used to combine timbres of 10 harmonics to form the vowel sounds A, E, I, O, and U. Driven by an intermittent electrical current, the tuning forks were made to vibrate using electromagnets. The forks would generate a fundamental frequency and overtones which could then be combined. The keyboard controlled a series of round shutters which covered the aperture of each resonator. When one pressed a key, that shutter would move, allowing the waves from the tuning fork to enter the resonator and produce a tone; the intensity could be adjusted by sliding the resonator closer to or farther from the fork.

With this device, Helmholtz showed that musical notes are composed of many different tones, and that the timbre of vowel sounds and musical notes is a result of their complexity. The device clearly demonstrated that the musical note not only contains "a simple 'fundamental' vibration... but also a 'harmonic series' of whole number multiples of this frequency called 'overtones'. Helmholtz proved, using this synthesizer, that it is the combination of overtones at varying levels of intensity that give musical tones, and vowel sounds, their particular sounds quality, or timbre." (Rees) Specimens of this device are extremely rare, with only one similar but smaller apparatus located in a US institution that we know of — we have not seen any others as large or finely made as this one. Max Kohl of Chemnitz is perhaps one of the most famous scientific instrument makers of the late 19th and 20th centuries. His work was distinguished by its exacting craftsmanship, and high quality materials. 

For a detailed description of how to operate this apparatus see: Appendix VIII "Practical Directions for Performing the Experiments on the Composition of Vowels" in: Hermann von Helmholtz. On the Sensations of Tone as the Physiological Basis for the Theory of Music. London: Longmann, Greens & Co, 1885; David Pantalony. Altered Sensations: Rudolph Koenig's Acoustical Workshop in Nineteenth-Century Paris. New York: Springer Science, 2009; Torben Rees. "'Helmholtz's apparatus for the synthesis of sound: an electrical 'talking machine.''' Explore Whipple Collections, Whipple Museum of the History of Science, University of Cambridge, 2010 [http://www.hps.cam.ac.uk/whipple/explore/acoustics/hermanvonhelmholtz/helmholtzssynthesizer/, accessed 23 October 2017]; Max Kohl Price List No. 50, Vols. II and III. Physical Apparatus. Vol. II. Chemnitz, Germany: Max Kohl, 1909, item 53,586, p. 460.