Helmholtz Sound Synthesiser. Max Kohl. Germany, 1905

Max Kohl AG, founded on 14 March 1876, was a well-known company that designed and built scientific, mechanical, and electrical instruments and was based in Andorfer Strasse, Chemnitz, Germany. The company developed a wide range of equipment sold worldwide to laboratories and universities, including a sound instrument based on a design by the German physicist and psychologist Hermann von Helmholtz.¹ Max Kohl Catalogue https://www.sil.si.edu/DigitalCollections/trade-literature/scientific-instruments/files/51637/index.htm accessed 02/11/2026 The Max Kohl AG factory in Chemnitz was destroyed by Allied bombing during World War II, and most of the remaining equipment was transported intact after the war to the Soviet Union.

The ‘Sound Synthesiser’ was not intended as a musical instrument but a scientific tool to demonstrate and analyse the effect of overtones in complex sound as described in Helmholtz’s revolutionary 1870 book Die Lehre von den Tonempfindungen als physiologische Grundlage für die Theorie der Musik ( ‘On the Sensations of Tone as a Physiological Basis for the Theory of Music‘ ) which had a huge impact on musicologists and instrument designers throughout the twentieth century. Using acoustic resonators, Helmholtz demonstrated that the components of complex sounds are a combination of overtones of a fundamental note (e.g. a “fundamental” pitch G 440Hz contains a harmonic series of whole number multiples of this  440Hz frequency or overtones – 880Hz G, 1320Hz, 1760Hz, etc., at variable volumes). ²Rees, Orben. (2010) ‘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.The Sound Synthesiser used a number of tuning forks that produced almost pure tones, driven by electromagnets, which in turn were amplified by a Helmholtz Resonator to generate overtones. The range of overtones could be ‘filtered’ by a mechanical shutter. The instrument helped in the understanding of the nature of speech and vowel sounds; vowel sounds being varied combinations of resonant overtones or ‘formants’ created by the muscles of the vocal tract.³Helmholtz, H.(1895) On the sensations of tone as a physiological basis for the theory of music, London, New York : Longmans, Green, and Co.

Many variations of Helmholtz resonators were built; some used brass spheres with hand-held tuning forks, while others employed electromagnets to excite the tuning forks. Max Kohl’s 1985 version had ten forks and their corresponding resonators attached to a 39½ x 29-inch mahogany base. The system is driven by an intermittent current supplied by a large horizontal master tuning fork and is operated by pressing keys on a small ivory keyboard, which transmits the current to the corresponding electrically driven tuning forks. The keyboard is marked; ut [Do, or C] to 4 octaves, mi [E] to 3 octaves, and sol [G] to 3 octaves. The synthesiser was capable of combining timbres of 10 harmonics to form multiple vowel sounds.