The ‘Pianorad’, Hugo Gernsback, USA, 1926

The Pianorad at WKNY

The Pianorad at WRNY

The Pianorad was a development of the Staccatone designed by Hugo Gernsback and built by Clyde Finch at the Radio News Laboratories in New York. the Pianorad had 25 single LC oscillators,one for every key for its two octave keyboard giving the instrument full polyphony, the oscillators produced virtually pure sine tones:

Hugo Gernsbacks' Pianorad

Hugo Gernsbacks’ Pianorad

“The musical notes produced by the vacuum tubes in this manner have practically no overtones. For this reason the music produced on the Pianorad is of an exquisite pureness of tone not realised in any other musical instrument. The quality is better than that of a flute and much purer. the sound however does not resemble that of any known musical instrument. The notes are quite sharp and distinct, and the Pianorad can be readily distinguished by its music from any other musical instrument in existence.”

Each one of the twenty five oscillators had its own independent speaker, mounted in a large loudspeaker horn on top of the keyboard and the whole ensemble was housed in a housing resembling a harmonium. A larger 88 non keyboard version was planned but not put into production. The Pianorad was first demonstrated on june 12, 1926 at Gernsback’s own radio station WRNY in New York City performed by Ralph Christman. The Pianorad continued to be used at the radio station for some time, accompanying piano and violin concerts.

Hugo Gernsback

Hugo Gernsback


Hugo Gernsback: “The ‘Pianorad’ a New Musical Instrument which combines Piano and Radio Principles” Radio News viii (1926)

The ‘Dynaphone’, René Bertrand, France, 1927


The French electrical engineer René Bertrand, who had been experimenting with electronic instruments as early as 1914, was a long time friend and collaborator with Edgard Varèse and with Varèses support Bertrand developed the “Dynaphone” (not to be confused with Cahill’s “Dynamophone” or “Telharmonium”). The Dynaphone was a portable, monophonic non-keyboard, dial operated vacuum tube oscillator instrument. The instrument was semi-circular in shape with a diameter 0f 30 cm played on top of a table. The Dynaphone belonged to a family of dial-operated non keyboard electronic instruments developed around the 1930′s such as Mager’s ‘Spharaphon.The right hand controlled the pitch using a circular dial on a calibrated disc (cardboard cut-out templates of music could be inserted). The total rotation of the dial was equal to seven octaves but only the five highest or lowest could be selected at any one time by the means of a switch, giving an overlap of three octaves common to both ranges. Vibrato effects could be added by moving the right hand to and fro slightly and the machine also included a push button for articulating the sound. The left hand controlled the volume and timbre – described as similar to a cello, low flute, saxophone or french horn.


A later development of the Dynaphone (known as the ” Radio-electric-organ” used a five octave keyboard on which the note played could be doubled at the fifth and octave.The first public demonstration of the instrument in 1928 was a performance of Ernest Fromaigeat’s ‘Variations Caractéristiques’ for six Dynophones and later in ‘Roses de Metal’ a ballet by the swiss composer Arthur Honegger

In 1932 Varèse applied to the Guggenheim memorial fund for a grant towards continuing the development of the Dynaphone:

Edgard Varese

Edgard Varese

Edgarde Varèse

“…..The Dynaphone (invented 1927-28) is a musical instrument of electrical oscillations similar to the Theremin, Givelet and Martenot electrical instruments. But its principal and operation are entirely different, the resemblance being only superficial. The technical results i look for are as follows:

  • To obtain pure fundamentals
  • By means of loading the fundamentals with certain series of harmonics to obtain timbres which will produce new sounds.
  • To speculate on the new sounds that the combination of two or more interfering Dynaphones would create if combined as one instrument.
  • To increase the range of the instrument to reach the highest frequencies which no other instrument can give, together with adequate intensity.

The practical result of our work will be a new instrument which will be adequate to the creative needs of musician and musicologist…..”

Despite Varèse’s assertions, the Dynaphone was not distinctly different from its close competitors and the Guggenheim Foundation did not sponsor Bertrands work despite several further attempts by Varèse.
In 1941, Edgard Varèse, in the hope to resume his collaboration with Léon Theremin, wrote him the letter reported below (courtesy of Olivia Mattis ), but the inventor wasn’t able to read it until 1989, when musicologist Olivia Mattis, during an interview with Theremin (first emerged from Russia after 51 years), presented a copy of it. The letter is dated May 5, 1941.

Dear Professor Theremin,

On my return from the West in October I tried to get in touch with you. I wanted very much to see you again and to learn of the progress of your work. I was sorry – on my account – that you had left New York. I hope that you have been able to go on with your experiments in sound and that new discoveries have rewarded your efforts.

I have just begun a work in which an important part is given to a large chorus and with it I want to use several of your instruments – augmenting their range as in those I used for my Equatorial – especially in the high range. Would you be so kind as to let me know if it is possible to procure these and where … and in case of modifications in what they consist. Also if you have conceived or constructed new ones would you let me have a detailed description of their character and use. I don’t want to write any more for the old Man-power instruments and am handicapped by the lack of adequate electrical instruments for which I now conceive my music.

Mr. Fediushine has kindly offered to forward this letter to you.

Please let me hear rom you as soon as possible.

With cordial greetings and best wishes in which my wife joins me,


Edgard Varese

P.S. If any of your assistants or collaborators are continuing your work in New York would you kindly put me in touch with them.


Edgard Varèse L.E.Gratia: ‘La Musique des Ondes éthérées’ , Les ménestrel, xc (1928)

The ‘Cellule Photo Electrique’. Pierre Toulon & Krugg Bass, France, 1927.

Pierre Toulon's Patent for the Cellulophone

Pierre Toulon’s Patent for the Cellulophone

Invented by the French engineer Pierre Toulon aided by the electronic engineer Krugg Bass, the Cellulophone (“Cellule Photo-électrique”) made it’s debut as a prototype in France in 1927. The Cellulophone was an electro-optical tone generator instrument resembling an electronic organ controlled by two eight octave keyboards and a foot pedal board.

The sound was created by passing a light beam through slits in a vari-speed rotating disk. The single spinning disk was cut with a number of equidistant slits (54 slits for the lowest note) with different shaped masks to create varied timbres. The disks masked a light beam that flashed through the slits and on to a photoelectric cell, the speed of the rotating disk therefore determining the frequency of the output signal from a single vacuum tube oscillator.

One disk was used for all the notes of each octave therefore notes whose frequencies could not be generated by an integral number were out of tune. This system however gave the unique and unusual possibility of having a different timbres for each octave. The Cellulophone was one of a generation of instruments in the 1920-30′s using a photo-electric sound generation method; other examples being the “Licht-ton Orgel” , the “Photona” and the “Radio Organ of a Trillion Tones”. The increased sophistication and reliability of post war electronic circuitry marked the decline of light based synthesis after the 1940′s except for a few pioneers such as Daphne Oram who used a similar sytem not only to synthesise sounds but to sequence sounds.

Pierre Toulon proposed in the 1930′s a related technique of speech synthesis using fragments of optical film mounted on a rotating drum.


Donhauser, P.: Elektrische Klangmaschinen. Die in Deutschland und Österreich Pionierzeit, Boehlau Vienna 2007.

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

Ondes Martenot

Ondes Martenot

Maurice Martenot a Cellist and radio Telegraphist, met the Russian electronic engineer Leon Termen in 1923, this meeting lead him to design an instrument based on Termens ideas, the first model, the “Ondes-Martenot” was patented on the 2nd of April 1928 under the name “Perfectionnements aux instruments de musique électriques” (improvements to electronic music instruments). His aim was to produce a versatile electronic instrument that was immediately familiar to orchestral musicians. The first versions bore little resemblance to the later production models: consisting of two table mounted units controlled by a performer who manipulated a string attached to a finger ring (using the bodies capacitance to control the sound characteristics in a manner very similar to the Theremin) this device was later incorporated as a fingerboard strip above the keyboard.

Female Ondes Orchestra

Female Ondes Orchestra

Later versions used a standard keyboard.The Ondes-Martenot became the first succesfull electronic instrument and the only one of its generation that is still used by orchestras today, Martenot himself became, 20 years after its invention, a professor at the Paris Conservatoire teaching lessons in the Ondes-Martenot. The Ondes-Martenot’s success was the Theremins loss, although both used the vacuum tube oscillator as a sound source and were both monophonic, where the Theremin had a sliding scale and no fixed preset notes the Ondes-Martenot had a keyboard and a strip control for glissando and vibrato, organ like stops for preset timbres and an appearance that was familiar to any keyboard player.

Pre-set sounds on the later Ondes Martenot were:

  • Onde (O): A simple sine wave timbre. 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 present in the signal by using a slider situated 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.

The sound from the instrument could be output to a number of speakers or ‘Diffuseurs’ who’s physical properties further coloured the sound, the were:

  • ‘Principal’ A traditional, large loudspeaker.
  • ‘Résonance’ A loudspeaker which uses springs to produce a mechanical reverb effect.
  • ‘Métallique’ A small gong is used as the loudspeaker diaphragm to produce a ‘halo’ effect rich in harmonics.
  • ‘Palme’ An iconic lyre-shaped loudspeaker, using strings to produce sympathetic resonances.

loudspeakers or Diffuseurs of the Ondes Martrnot: the Métallique, the palm and the Principal

The instrument also had a bank of expression keys that allowed the player to change the timbre and character of the sounds. A later (1938) version of the instrument featured microtonal tuning as specified by the Hindu poet Rabindranath Tagore and the musician Alain Danielou. The Ondes-Martenot was quickly accepted and became one of the few electronic instruments to be admitted to the orchestra (at least in France) and had a wide repertoire by prominent composers such as Edgard Varèse, Olivier Messian (The “Turangalîla Symphonie” and “Trois Petites Liturgies de la Presence Divine” amongst others ), Darius Milhaud , Arthur Honegger, Maurice Jarre, Jolivet and Koechlin.


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

 “Whoever has occupied himself even a little with electric sounds will be forced to the conclusion: there are yet things in music of which our book-learning cannot dream.” Jörg Mager

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 Ferruci 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.

The Klaviatursphäraphon

The Klaviatursphäraphon

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.

Jorg Mager and the The Partiturophon

Jorg Mager and the The Partiturophon

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.

The Kaleidophon

The Kaleidophon

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.


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

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 ‘Givelet’ or ‘Coupleux-Givelet Organ’ Armand Givelet & Edouard Eloi Coupleux, France. 1930

Armand Givelet & Edouard Coupleux at the paper-punch controls of the 'Givelet'

Armand Givelet & Edouard Coupleux at the paper-punch controls of the ‘Givelet’ c1932

The last instrument of the Givelet – Coupleaux collaboration was the ‘Coupleaux -Givelet Organ’ or ‘Givelet’. The Givelet was a unique instrument that combined vacuum tube oscillators with a sound control system using a punched paper roll in a way similar to a player piano to define the sound synthesis. Pitch, volume, attack, envelope, tremolo and timbre could be controlled by cutting and splicing paper rolls and like the “Wave Organ“, the Givelet was polyphonic. The technique of using punched paper “programs” was not exploited until fifteen years later in the 1950′s with the RCA Synthesiser.  Givelets and Coupleaux’s instrument was designed to be a commercial and cheap replacement for pipe organs and utilise the ability for ‘silent recording’ or direct injection into radio transmitter. The Givelets were installed in churches around France and at a broadcasting radio station in Paris. The Givelet eventually lost out commercially to the more efficient and less complex  Hammond Organ.

Givelet of 1930

The Givelet-Coupleux Organ of 1930 played by Armand Givelet

Patent Documents


A.J.Givelet: ‘Les Instruments de Musique à oscillations électriques: Le Clavier à Lampes ‘, Génie civil, xciii(1928)

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

The Hellertion

The Hellertion

The Hellertion (1929)

The Hellertion,christened after the combination of the inventors names, was a monophonic vacuum tube instrument developed collaboratively by Peter Lertes, an electrical engineer in Leipzig and Bruno Helberger, a well known pianist of his time. Several variants of the instrument were constructed with the assistance of Schneider-Opel in Frankfurt, Germany the last of which was known as the Heliophon.
The Hellertion was the first electronic instruments to use a fingerboard/continuous controller instead of a keyboard manual and was much copied in other later instrument designs such as the Trautonium and the Sonar. The fingerboard was 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.
Hellberger and Lertes at the Hellertion

Hellberger and Lertes at the Hellertion

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.
The four-slider controls of the Hellertion

The four-slider controls of the Hellertion

Diagram showing the sliding control of the Hellertion.

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

The Helliophon (1936)

A development of the Hellertion by Bruno Hellberger. The first version of the Heliophon was completed in Berlin, 1936 but destroyed during WW2. Hellberger continued the development after the war and built a second model in 1947 in Vienna, Austria and continued the development of the Heliophon until his death in Vienna in 1951 (subsequent development was taken over by Woflgang Wehrmann). 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.The Heliophon was used by Hellberger throughout the 1940′s and 50′s for theatrical and musical productions, the instrument was said not only to be capable of producing realistic imitations of orchestral instruments but able to imitate  human vocal sounds.


A survey of ‘modern’ electronic instruments was published by Peter Lertes in 1933: “Elektrische Musik:ein gemeinverständliche Darstellung ihrer Grundlagen, des heutigen Standes der Technik und ihre Zukunftsmöglickkeiten” (Dresden & Leipzig, 1933)J.Marx:”Heliophon, ein neues Musikinstrument”, Ömz,ii(1947),314

 “Das Hellertion, ein neues electrisches Musikinstrument,” Funkbastler, July 3, (1931).