1920 –1930 – Page 3 – 120 Years of Electronic Music

The ‘Ondes-Martenot’. Maurice Martenot, France, 1928

The 3rd Model Ondes Martenot circa 1929. Image: © Claude Germain. Philharmonie de Paris: Musée de la musique, Fonds Martenot, E.982.9.1. — The 3rd Model *Ondes Martenot*, circa 1929. Image: © Claude Germain. Philharmonie de Paris: Musée de la musique, Fonds Martenot, E.982.9.1.

The Ondes Martenot, also known as the Ondes Musicale Martenot or simply the “Ondes,” is an early monophonic electronic musical instrument created by Maurice Martenot (1898-1980), a cellist and former World War I radio operator. Martenot’s instrument became one of the few early electronic musical instruments to enter commercial production and gain recognition in the canon of 20th and 21st-century music, particularly within the French new music movement of the 1930s and 1940s.

The Ondes was one of several electronic instruments developed after the First World War that utilised the heterodyning vacuum-tube effect to produce audible tones. Notable examples include Lev Termen’s Theremin (patented in 1928), Friedrich Trautwein’s Trautonium (patented in 1930), and Jorg Mager’s Elektrophon (patented in 1921), all of which were based on similar military radio technology. This method of electronically generating sound remained the predominant technique until the advent of integrated circuits in the 1960s.

While serving as a radio operator in the French army during the final years of World War I, Martenot began to realise the potential of electronic sound. By manipulating the radio feedback howl that plagued early radio transmitters and receivers, Martenot was able to play simple tunes ¹ —a trick he referred to as the “Mexican singing dog”— much to the amusement of his fellow troops. Once demobilised, Martenot put this experience into practice and began experimenting with designs for his new electronic instrument.

Maurice Martenot plays the 1928 *Ondes no 1*. Image Philharmonie de Paris: Musée de la musique, Fonds Martenot, E_2019_9_1_6_1_82_P0001

Close-up of the 1928 *Ondes Martenot*. Image Philharmonie de Paris: Musée de la musique, Fonds Martenot, E_2019_9_1_6_1_81_P0001.

The first versions bore little resemblance to later production models and consisted of two table-mounted units in which the machine’s pitch was controlled by body capacitance, in a manner very similar to the Theremin. Based on a pair of heterodyning vacuum tubes, the Ondes produced a single, continuous monophonic tone similar to a sine tone but with added harmonic distortion from the vacuum tubes. The second model, known as the Ondes-Martenot, was patented on the 2nd of April 1928 under the title Perfectionnements aux instruments de musique électriques (improvements to electronic musical instruments). ², in this model, the player, in a standing position, controlled the pitch with a string attached to a ring held in the performer’s hand, giving a continuous tonal glissando. Martenot first demonstrated the Ondes Martenot on April 20, 1928, as a soloist performing Dimitrios Levidis’s Poème symphonique at the Paris Opera. This model was quickly succeeded by the third model in 1929, which had a fixed, non-functioning printed 7 octave keyboard to guide the player to the relevant pitch using either the string controller or a finger-guard device held in the player’s hand. This third model, created in collaboration with the engineer Maurice du Breuil, featured a dual-speaker set housed in a framed box and a set of expression controls accessed via a left-hand sliding drawer.

The 1929 model 2 Ondes Martenot showing the ribbon controller placed above a fixed wooden keyboard marker.Close-up of the 1928 Ondes Martenot. Image Philharmonie de Paris: Musée de la musique, Fonds Martenot, E_2019_9_1_6_1_10_P0001. — The 1929 model 2 *Ondes Martenot* showing the ribbon controller placed above a fixed wooden keyboard marker. Image: Philharmonie de Paris: Musée de la musique, Fonds Martenot, E_2019_9_1_6_1_10_P0001.

The Ondes Martenot underwent several design improvements throughout the 1920s, ultimately stabilising with the modèle 37, which was introduced in 1931. Maurice Martenot aimed to create a versatile electronic instrument that would be familiar to orchestral musicians while distinguishing it from competitors, such as the Trautonium and the Theremin.

The 1931 modèle 37 Ondes. Image: Philharmonie de Paris: Musée de la musique, Fonds Martenot,E_2019_9_1_6_1_8_P0001-medium

The modèle 37 was the first to feature a standard keyboard that could be played alongside a string controller known as the ‘ruban,’ which allowed for pitch glissandi. This new model incorporated features that would shape the design direction for subsequent versions. These features included two left-hand pitch controllers: a suspended vibrato device called the clavier and the aforementioned ruban, which runs parallel to the keyboard and allows for tonal and timbral glissandi. Additionally, it had a left-hand-controlled prismatic touche d’expression, which modulated the sound envelope.³ Une invention ‘essentiellement française’: seeing and hearing the Ondes Martenot in 1937, MUSIQUE – IMAGES – INSTRUMENTS N° 17, BNF, Paris, 107.

After a world tour promoting his instrument, Maurice Martenot developed an interest in the timbres of non-Western music, particularly the metallic sounds of the Javanese and Balinese gamelan. To replicate these sounds, Martenot dedicated the next decade to introducing various acoustically resonant loudspeakers, known as Diffuseurs, which enhanced the tonal richness of the instrument’s output. These include:

– Principal: A standard, large loudspeaker.
– Résonance: A loudspeaker that utilises springs to create a mechanical reverb effect.
– Métallique: A small gong serves as the diaphragm of this loudspeaker, producing a ‘halo’ effect rich in harmonics – introduced in the 1937 model.
– Palme: An iconic lotus-shaped loudspeaker that uses tuenable strings to generate sympathetic resonances – introduced in 1948 models.

The 1937 microtonal *Ondes* designed for Rabindranath Tagore. Image Philharmonie de Paris: Musée de la musique, Fonds Martenot

Martenot also collaborated with the Indologist Alain Danielou to create a microtonal version of the instrument, designed for the renowned Hindu poet Rabindranath Tagore. This microtonal ondes of 1937 (Patent 841.128 February 1939) was shorter than the standard version and featured a 5-octave keyboard. According to Laurendeau, it included a set of control discs placed above the keyboard, allowing simultaneous tuning of notes such as C and D to the twelfth. This setup ensured that the overall keyboard tuning corresponded to the raga mode. Laurendeau, Jean. (1990) Maurice Martenot, Luthier de l’électronique, Dervy-Livres, 100.[/mfn]

The range of resonant loudspeakers or Diffuseurs of the 1931 Ondes Martenot: (L-R) the Métallique (1937) , the Palme (1948) and the Principal.

The modèle 37 Ondes-Martenot was unveiled at the 1937 Paris Expo, an exhibition of art and industry held from May to October 1937. A key feature of the expo was a program of 46 musical events featuring prominent French and European composers, including Milhaud, Messiaen, Vellones, Honegger, Ibert, Schmitt, Koechlin, and others. These performances were broadcast throughout the event via loudspeakers positioned along the Seine River, attached to the Eiffel Tower, and even from aeroplanes flying over the city. The ondes-martenot gained a certain cult status during the Expo, being described in the event catalogue as “a new source of infinite artistic joy” and “the most sensational musical and scientific achievement of the 1937 exposition.” Eleven out of the eighteen composers commissioned to create works for the Expo wrote compositions specifically for the ondes. Among these was Ginette Martenot’s all-female electronic ondes orchestra, which frequently performed Messiaen’s commissioned piece, Fête des belles eaux. This performance was enhanced by a spectacular display of illuminated fountains and coloured lights, choreographed and synchronised to the music.

Geneviève “Ginette” Martenot’s electronic ondes orchestra at the 1937 Paris Expo. Image: Philharmonie de Paris: Musée de la musique, Fonds Martenot E_2019_9_1_6_1_96_P0001

During the 1930s, Martenot enhanced the instrument by introducing features such as the ability to modify and simultaneously combine different sound waveforms using a set of control sliders in the left-hand sliding drawer. The later models of the Ondes included pre-set sounds that were:

- - Onde (O): A simple sine wave. Similar in sound to the flute or ocarina.
  - Creux (C): A peak-limited triangle wave. Similar in sound to a clarinet in high registers.
  - Gambe (G): A timbre somewhat resembling a square wave. Intended to be similar in sound to string instruments, as the French title would suggest.
  - Petit Gambe (g): A similar but less harmonically-rich timbre than Gambe. The player can control the number of harmonics in the signal using a slider in the control drawer.
  - Nasillard (N): A timbre resembling a pulse wave. Similar in sound to a bassoon in low registers.
  - Octaviant (8): A timbre with a reinforced first harmonic whose intensity in the signal can be controlled by using a slider. This setting is analogous to the 4-foot stop in organ terminology.
  - Souffle (S): A timbre often described as white noise, but in fact pink noise of indefinite pitch.

With the introduction of transistors in the 1960s, Martenot developed an integrated circuit version of the instrument, followed by a digital version in the 1980s.

The Ondes Martenot is one of the few electronic musical instruments that have been embraced by the classical music world. It boasts a wide repertoire of works composed for it by prominent composers such as Edgard Varèse, Olivier Messiaen (including Turangalîla-Symphonie and Trois Petites Liturgies de la Présence Divine), Darius Milhaud, Arthur Honegger, Maurice Jarre, André Jolivet, Pierre Boulez, and many others.

Sources:

1
such as Debussy’s “Clair de Lune.” Laurendeau, Jean. (1990) Maurice Martenot, Luthier de l’électronique, Dervy-Livres, 48. ↩︎
2
French patent FR666807A ↩︎
3
Asimov, Peter. (2018) Une invention ‘essentiellement française’: seeing and hearing the Ondes Martenot in 1937, MUSIQUE – IMAGES – INSTRUMENTS N° 17, BNF, Paris, 107. ↩︎

The Electrophon (1921), Sphäraphon(1924), kurbelsphärophon (1926), Klaviatursphäraphon(1928), Partiturophon (1930) and Kaleidophon(1939). Jörg Mager, Germany.

Jörg (Georg Adam) Eichstätt Mager born November 6, 1880 Aschaffenburg, Bavaria, Died Aschaffenburg 1939 — Jörg (Georg Adam) Eichstätt Mager born: November 6, 1880 Aschaffenburg, Bavaria, Died: Aschaffenburg 1939

Jörg Mager, the German inventor and self proclaimed ‘Father of German Electronic Music’ was an important figure in the development of electronic musical instruments. ¹ From around 1921 until his death in 1939 he created a family of electronic instruments that included the Electrophon (1921), Sphäraphon(1924), kurbelsphärophon (1926), Klaviatursphäraphon(1928), Partiturophon (1930) and Kaleidophon(1939). Central to Mager’s design concept was the pursuit of a utopian perfect musical instrument, one that could deliver on the microtonal promises outlined in Ferrucio Bussoni’s influential text Entwurf einer neue Ästhetike der Tonkunst (‘Sketch of a New Esthetic of Music’, published in Germany in 1907 and 1917, and in English translation in New York in 1911). Busoni argued that music needed new instruments to provide a new sonic palette – instruments that had a wider tonal and timbral range than the classical instrumentarium: “So narrow has our tonal range become, so stereotyped its form of expression”.²

Jörg Mager’s lifelong fascination with micro-tonal music began accidentally during the hot summer of 1911 when he heard an out of tune organ playing notes beyond the fixed tempered scale. Fascinated by the instruments strange sounds he began to explore the concepts of half and quarter tone music which he eventually self-published in his Vierteltonmusik of 1915. At the same time he began to design an instrument that was capable of delivering micro-tonal and quarter tone scales, the first of which was an acoustic harmonium, the Vierteltonharmonium (Four-Tone harmonium) in 1912.

After his participation in the failed 1918 communist coup in Bavaria, Mager left for Berlin. Here he joined a small circle of microtonal musicians (Mager, Alois Hába, Richard Stein, Ivan Wischnegradsky ) under the wing of renowned composer and theorist Ferrucio Bussoni. This circle of musicians were united in their aim to liberate music from the tyranny of fixed-tonality, however, rather than adapt existing instruments, Mager decided to create an entirely new instrument based on the emerging radio technology of the time.

To survive in post WW1 hyper-inflationary Berlin, Mager accepted any unskilled labour he could find. It was while working in a radio vacuum tube factory that he hit upon the idea of using vacuum tubes as the basis for his first electronic microtonal instrument, the Electrophon in 1921. The Electrophon was a simple monophonic instrument based on the same heterodyne principal as that of the Theremin; a method by which two frequencies are combined within the radio frequency spectrum (not perceptible by the human ear) to produce a third frequency that is equal to the difference between the latter two frequencies and that itself is within the audible spectrum humans. In case of Electrophon two 50 Khz frequency oscillators were used. The novel feature of the Electrophon was that rather than being controlled by a fixed tone manual, notes were instead triggered by rotating a metal handle, creating a glissando type effect on a continuous tone. Under the handle was a semicircular plate marked with chromatic scale intervals. Changes in timbre could be applied through various filters. Further developments of the Electrophon were christened the Sphärophon after the Pythagorean legend of the music of the spheres.

“The music of the future will be attained by radio instruments! Of course, not with radio transmission, but rather direct generation of musical tones by means of cathode instruments! […] Indeed, the cathode-music will be far superior to previous music, in that it can generate a much finer, more highly developed, richly coloured music than all our known musical instruments! ”
Jörg Mager: ” Eine Neue Epoch Der Music Durch radio” (Berlin 1924)

Mager’s proposal in ” Eine Neue Epoch…” was that the medium of radio should be used to create and deliver a new type of utopian ‘free’ music by means of new electronic cathode-ray musical instruments, rather than just a means of transmitting mass content:

“…Radio firms have mobilised more energy for transmission of a radio-music but have hardly shown any interest in the most important problem: the production of music itself.”

“…the music of the future will be implemented largely by radio instruments not only in the sense that they can be easily transmitted, but especially that musical sounds can be produced directly through cathode-ray instruments . “

Mager’s fellow Microtonalist Czech composer Alois Hába added:

“This is a new era in the development, not only in building instruments, but in music in general . “

Further developments of the Sphärophon lead to the kurbelsphärophon unveiled at the 1926 Donaueschingen summer music festival (alongside Leon Termen’s Theremin). This adaptation added a second manual dial that allowed the player to interrupt the instrument’s continuous output and avoid the continuous glissando of the Sphärophon by queuing up another note and added two pedals to control each note’s volume and envelope.

Mager playing the kurbelsphärophon — Mager playing the Kurbelsphärophon

Though mostly ignored at the time, Mager’s instrument quickly gained notoriety throughout Germany; the composer Georgy Rimsky-Korsakov (Grandson of the Russian composer) composed some quarter-tone experimental pieces and Paul Hindemith enthusiastically endorsed Mager’s instrument. This support lead to the the formation in 1929 of the ‘Studiengesellschaft für Elektro Akustische Musik’ (‘Society for Electro-acoustic Music) in Darmstadt to support his research (funded by the city of Darmstadt, the Heinrich Hertz Institut für Schwingungsforschung and the Reichsrundfunk radio station) . The society was housed in a large, luxurious castle in Darmstadt and staffed with skilled technicians including the future electronic instrument designer Oskar Vierling.

With this resource at his disposal Mager continued to develop his instrument design, creating the Klaviatursphäraphon in 1928. In this model he replaced the handles of the Kurbelsphäraphon with two short keyed monophonic keyboards – the shorter keys allowing the player to play both keyboards simultaneously thereby producing a duophonic tone. It was also possible by adjusting the capacitance of the sound generating circuit to alter the intervals between each key and scale the acoustic length of the keyboard. An octave could be made as small as a major second, so that each successive step represented an interval of a 12th tone. Additional tone colour was added by mechanical resonators, series of filters and specially formed resonant speakers.

By now, Mager’s focus was moving from micro-tonality towards audio timbre. The “Partiturophon” (from the German ‘Partitur’ or musical score, reflecting his aim of capturing the varied combinations of orchestral timbre) was a four (in later models, five) keyboard and five voice version of the Klaviatursphäraphon produced in 1930. This instrument allowed the player to play four (or five) voices at once, one voice per keyboard:

“Mager produced today and organ with many registers on which four voice playing is possible. So far there is only one difficulty; that is, that each voice must have its own keyboard, thus the four voice movement must be played on three manuals and the pedal. For this reason the manuals must be close to each other and the keys short, so that one can easily play on several manuals with one hand. For this reason the keys are somewhat narrower than those on a regular organ or piano keyboard. Apart from these difficulties, which require a special adjustment to the playing of the new instrument, it is surprising in its infinite multiplicity of sound possibilities, through dynamic wealth of shading and through the possibilities of expression in the tones”

The critic and historian Frederick Prieberg on the Partiturophon

1932 marked the high point of Mager’s success. He had become a household name in Germany and received commissions, from Winifred Wagner herself, to provide the sound effects for the annual Beyreuth Wagner festival, and he was also commissioned to mark the centenary of Gothe’s death with a micro-tonal piece for thirty theatrical interpretations of drama Faust , which took place in Frankfurt and Darmstadt. Other plaudits came from composers and conductors Arturo Toscanini and Wilhelm Furtwängler , the latter the director of the orchestral interpretation of Parsifal in 1931.

Yet this success was short lived. A new electronic instrument had emerged in 1930; Dr Friedrich Trautwien’s ‘Trautonioum’. In contrast to Mager’s amateur enthusiasm, Trautwien was a trained engineer and managed to produce an instrument that was both novel, reliable and wasn’t shackled by the complexity of Mager’s devotion to micro-tonality. The final blow to Mager came in 1933 when Hitler’s National Socialists took power. Experimental music was labelled ‘Entartete’ or ‘degenerate’ and un-German; the great flowering of German musical innovation had come to an abrupt end. Mager tried to ingratiate himself into the new party “to get on the gravy train” but became increasingly paranoid and irritable, driving away many of his collaborators and supporters. In the struggle to develop the Partiturophon as a commercial domestic instrument, the contract for the ‘Studiengesellschaft für Elektro Akustische Musik’ lapsed and funding dried up. Mager spent the rest of his life leading an impoverished semi-nomadic existence. His state of health was increasingly precarious due to diabetes and growing disorientation and mental confusion. His daughter Sofie, brought him back to Aschaffenburg, where he died on April 5, 1939, at the age of 59.

spite the oppressive new political climate, Mager was commissioned to create sound effects with the Partiturophon in the 1936 film "Stärker Paragraphen als" by Jürgen von Alten , with music by Rudolf Perak. — spite the oppressive new political climate, Mager was commissioned to create sound effects with the Partiturophon in the 1936 film “Stärker Paragraphen als” by Jürgen von Alten , with music by Rudolf Perak.

None of Mager’s instruments are known to have survived the Second World War, The castle at Darmstadt was heavily bombed by the Allies, obliterating the last traces of the Partiturophon and it’s predecessors. The last of Mager’s family of instruments was the Kaleidophon completed in 1939 and only survives in notes as “…a monophonic electronic instrument with kaleidoscopic sound mixtures following the tonal precepts of Arnold Schoenberg and Ferruccio Busoni.”

Mager's colleague Alois Hába playing the Partituropohn — Mager’s colleague Alois Hába playing the Partituropohn

Mager’s instruments ultimately failed because of, on one hand, Mager’s single minded devotion to microtonality which had virtually no repertoire and was little accepted even by the avant garde of the time ( even Mager’s close circle of friends Hába, Wischnegradsky and Stein never realised their promises to compose for the instruments) and on the other, the fact that the instruments were in continual development, unstable and never completely finished making it difficult to become anything more than an interesting curiosity.

Sources

Jörg Mager: ” Eine Neue Epoch Der Music Durch radio” (Berlin 1924)

http://acousmata.com/post/27443169341/jorg-mager

http://www.audionautas.com/2010/10/jorg-mager-el-genio-hurano-i.html

Peter Donhauser, “Electric sound machines. Pioneer days in Germany and Austria,” Böhlau Verlag, ISBN 9783205775935

Fred Prieberg, “Music in the Nazi state,” Dittrich Verlag, ISBN 392086266XElena monster, “As the electronic music was ‘invented’ ,” Schott Verlag, ISBN 3795718910

MAGER Jörg: Eine neue Epoche der Musik durch Radio, Berlin-Neukölln 1924. : Vierteltonmusik, Aschaffenburg [1915].

The ‘Hellertion’ and The ‘Heliophon’. Bruno Helberger & Peter Lertes, Germany, 1929-1936.

The Hellertion (1929)

The Hellertion, (sometimes Helertion ) christened after the combination of the inventor’s names, was a monophonic vacuum tube instrument developed collaboratively by Peter Lertes, an electrical engineer in Leipzig and Bruno Helberger from Frankfurt, a well-known pianist of his time. Helberger was inspired to build the instrument after witnessing Termen’s Theremin – possibly at the Neue Frankfurt exhibition in 1927. ¹ Several variants of the instrument were constructed and promoted through a licensing arrangement with the Schneider-Opel AG radio company in Frankfurt, who positioned the new instrument as ‘a portable, multi-voice instrument that can be connected to any radio with record amplification’. Although the deal eventually fell through with the collapse of Schneider-Opel in 1932, the Hellertion can be seen as the world’s first commercially produced electronic musical instrument.

Bruno Hellberger at the Hellertion — Bruno Helberger with an early version of a single voice the Hellertion designed as a grand piano attachment.

The Hellertion was the first electronic instruments to use a fingerboard / continuous controller instead of a keyboard manual a feature that was to influence the design of later electronic instruments particularly Trautwein’s Trautonium (essentially a licensed derivation of the Hellertion, a fact confirmed by the backplate of the 1930 version of the Trautonium recognising Lertes & Helberger’s patent) and the soviet instrument called the Sonar.

The Helberger-Lertes patent acknowledgment on the back of the Trautonium ELA T42

The fingerboard consisted of a flat metal resistance strip covered in leather which when pressed completed a circuit. Depending on where the strip is pressed, a different resistance in the circuit is created altering the voltage sent to the oscillator and thereby producing different pitches. The force of the pressure controlled the volume of the output signal. The fingerboard was marked to help the performer find the correct pitch on the strip and had a range of approximately five octaves.

The wire manual of the *Hellertion* with an added key reference guide. (image; Radio Wien. 1932)

Helberger and Lertes at the 4 voice version of the *Hellertion* 1932. (image; Radio Wien. 1932)

The original instrument had just one fingerboard strip which was gradually increased to four and then on the later models, six aligned in parallel horizontally at the height of a piano keyboard. The four and six strip models allowed four and six voice polyphony when the strip could be played simultaneously with fingers and thumbs. The Hellertion was occasionally used in concerts as a piano addition, the melody being played with one hand on the Hellertion and the accompaniment being played with the other hand on the piano. A version of the Hellertion was produced in 1931 microtonally tuned to 10 divisions of an octave.

Diagram showing the sliding control of the Hellertion. — Diagram showing the sliding control of an early model of the *Hellertion*.

peter_lertes_02 — Peter Lertes’ book on Electronic Music “Elektrische Musik. Eine gemeinverständliche Darstellung ihrer Grundlagen, des heutigen Standes der Technik und ihrer Zukunftsmöglichkeiten, etc” 1933.

The Hellertion premiered at a broadcast at Südwestdeutsche Rundfunk (SDR) on 20 November 1930 with where it was described as a new electro-acoustic instrument could be used ‘not just for Hausmusik (domestic music ensembles) but also for soundtracks for films’ and ‘a serious competitor to the cinema organ’.³ However the tone quality of the instrument was criticised especially the tone-slip of the player on the wire-controller ‘could be tormenting for the ear’.⁴

Patent documents of the Hellertion

The Heliophon (1936)

Bruno Helberger's 'Heliophon' — Bruno Helberger’s ‘Heliophon’

At the outbreak of war where around 1940 began constructing an enhanced version of the Hellertion he called the Heliophon. Helberger continued the development of the Hellertion creating an enhanced keyboard version of the Hellertion he called the Heliophon. The first version of the Heliophon was completed in Berlin, 1936, but destroyed during WW2. Helberger moved to Hörzendorf in Austria where he constructed a second model Heliophon in 1947 and continued the development of the instrument until his death in Vienna in 1951 (subsequent development was taken over by Wolfgang Wehrmann).

*A later 1950s (?) version of the Heliophon From the collection of Technisches Museum Wien. Image: (c) Technisches Museum Wien*

The sound of Heliophon was produced, as with the Hellertion, by heterodyning vacuum tube oscillators but with the Heliophon the sound was controlled by two 58 note pressure sensitive keyboard manuals instead of a series of fingerboard strips. Each keyboard had the ability to be split into three different pitches and timbres simultaneously, the output volume being controlled by foot pedals with a knee lever to add vibrato. Each keyboard had a Hellertion style fingerboard to add glissando and timbre variations which gave the instrument a remarkable versatility, apparently capable of producing realistic imitations of orchestral instruments as well as imitate human vocal sounds. The Heliophon was used by Helberger throughout the 1940s and ’50s for theatrical, film and musical productions.

The Heliophon on the soundtrack to Leopold Rudolf’s Der Rabe 1951

Helberger’s patent documents for the Heliophon

Sources:

1
Donhauser, Peter, Elektrische Klangmaschinen. Die Pionierzeit in Deutschland und Österreich, Böhlau, Wien, 2007, 46. ↩︎
2
“Elektrische Musik: Ein gemeinverständliche Darstellung ihrer Grundlagen, des heutigen Standes der Technik und ihre Zukunftsmöglickkeiten”, Theodor-Steinkopff-Verlag, Dresden & Leipzig, 1933 ↩︎
3
“Das Hellertion, ein neues electrisches Musikinstrument,” Funkbastler, July 3, (1931). ↩︎
4
Donhauser, Peter, Elektrische Klangmaschinen. Die Pionierzeit in Deutschland und Österreich, Böhlau, Wien, 2007, 49. ↩︎