In 1895 Thaddeus Cahill submitted his first patent for the Telharmonium “The Art of and Apparatus for Generating and Distributing Music Electrically”. The Telharmonium can be considered the first significant electronic musical instrument and was a method of electro-magnetically synthesising and distributing music over the new telephone networks of victorian America.

This first patent was initially rejected by the patent office because the “plan contained principles and practices found in other patented devices”. Cahill, a trained lawyer, eventually succeeded in having his patent accepted in 1897.

The first design of the instrument set out the principles of the ‘Telharmonium’ or ‘Dynamophone’ that would be developed by Cahill over the next twenty years. Cahill’s vision was to create a universal ’perfect instrument’; an instrument that could produce absolutely perfect tones, mechanically controlled with scientific certainty. The Telharmonium would allow the player to combine the sustain of a pipe organ with the expression of a piano, the musical intensity of a violin with polyphony of a string section and the timbre and power of wind instruments with the chord ability of an organ. Having corrected the ‘defects’ of these traditional instruments the superior Telharmonium would render them obsolete.

The other innovative aspect of Cahill’s design was that he proposed to distribute the electronic musical output of the instrument over the newly established telephone network to subscribers at home or in hotels and public spaces; hence the name ‘Telharmonium’ – ‘Telegraphic Harmony’. This was partly due to the fact that the only way of hearing the instrument in the pre-amplifier and loudspeaker era was via an acoustically amplified telephone receiver.

Influences

In 1885 Hermann Helmholtz’s ‘On the Sensations of Tone’ (1862) appeared in English translation and had an immediate and profound impact on scientific and musical thinking. Helmholtz defined the concept that a tone was composed of a single fundamental sound which, combined with a set of higher sounds, gave each musical tone a unique quality or timbre – and that these tones were a collection of ‘pure’ sine tone. Cahill’s reasoning was that the ‘perfect instrument’ could be built to created sine tones that could be combined to recreate the qualities of existing instruments without their ‘defects’.

The idea of transmitting music over he telegraphic or Telephone network was not new. Cahill was well aware of previous inventions and experiments with Telegraphic music.

As far back as 1809,the Prussian anthropologist, paleontologist and inventor Samuel Thomas Soemmerring created an electrical telegraph that triggered an array of tuned bells from a distance of several kilometres. This experiment was originally as an intended as an investigation into human consciousness and perception but led to speculation about the possibilities of transmitting music electronically over great distances.

In 1893 the Hungarian engineer and inventor Tivadar Puskás established the ‘Telefonhírmondó’ or ‘Telephone Herald’ a type of telephone based newspaper that broadcast music and news over the telephone network in Budapest to as many as 91,000 subscribers which continued (in tandem with a radio service) until World War II when the wire network was destroyed.

In Paris, Clément Ader created the ‘Théâtrophone’ a type of early binaural or stereo audio transmission of music and theatre in 1881 which ran until it was superseded by radio in 1931 and similarly, in London in 1895, the ‘Electrophone’ service distributed music hall and light music to an audience of subscribers.

But probably the biggest technical influence on Cahill was Elisha Gray’s ‘Musical Telegraph’ of 1874. Gray, one of the inventors of the telephone, had developed a way of transmitting pitched tones over a long distance telegraph network using electromagnetically controlled vibrating metal reeds. Gray had originally intended to use this as a way of sending multiple messages over a network ( a predecessor of multiplex signals) and had created a musical keyboard instrument to promote his ideas. It was the similarity of Gray’s work to Cahill’s initial concept that led to the rejection of Cahill’s first patent and in response Cahill was scathing about Gray’s instrument declaring that the Musical Telegraph was:

“practically useless. No person of taste or culture could be supposed to derive any enjoyment from music rendered in poor, harsh tones, with uneven power, and absolutely without expression or variation.”

…and that Gray’s patented machine was unable to produce sine waves or complex harmonics of the Telharmonium;

“…do not produce undulations of current; they produce sharp, violent (tones). (The device) unavoidably adds to the partials desired many which are injurious — so many, that his patent . . . seems … to wholly break down.”

Cahill restructured his patent to accentuate the differences between his invention and that of Elisha Gray – nevertheless, Gray’s ‘Musical Telegraph’ clearly had a major influence on Cahill’s new instrument.

The ‘Telharmonium’ or ‘Dynamaphone’

Cahill’s major criticisms of Gray’s ‘Musical Telegraph’ was that by using electromagnetically oscillating metal reeds, Gray’s instrument only had enough power to be heard at close range to a telephone receiver and, the Musical Telegraph’s oscillators could only create harsh, simple tones that lacked character and expression. Cahill’s proposal was to generate complex mixtures of sine tones using multiple electrical dynamos that would be powerful enough to be audible to an audience from a distance.

The core of his invention was the tone wheel; essentially a rotor with variably shaped alternators that spun within a magnetic field (The early versions used rheotomes; a set of brushes that contacted the rotor as it spun.) to generate a tone. Each tone wheel was composed of the fundamental tone and six ascending partials. The first model consisted of a mainframe of twelve identical rotors each of the twelve pitch-rotors carried seven fundamental alternators, six third-partial alternators, and five fifth-partial alternators. These rotors were spun at the relevant speed by a belt driven motor, giving the instrument a six octave range. This arrangement gave the Telharmonium two tuning systems; one being a pure harmonic series used for building the timbre of each note, and the other, an equal tempered scale used for combining notes into a scale.

The output quality of the tone wheels – especially with the rheotome versions – was harsh and unpleasant. The sound quality was softened by passing the signal through a series of secondary induction coils that filtered the harshness from the sound to a tone approximating a sine wave. (These induction could could also be controlled by the velocity of the keyboard, allowing the musicians a complex level of expressive influence over the tone.). Cahill was able to dispense with these purifying circuits in later models after perfecting rotor teeth cutting techniques to provide an almost pure sinusoidal output.

The number of partials for each fundamental could be controlled with familiar organ like stops allowing the instrument to imitate orchestral instruments. In this way, the Telharmonium was the first additive synthesiser; recreating instrumental timbres by adding and mixing harmonics.

Less familiar was the keyboard arrangement; for the second Telharmonium, Cahill hired the pianist Edwin Hall Pierce to develop a repertoire for the instrument as well as create sounds from the multiple harmonics. Pierce, with Cahill, also defined the unusually complex keyboard arrangement. Because the Telharmonium mechanically created notes using exact divisions that equated to just intonation, Pierce decided to use three sets of keyboards (two or sometimes four in later models) that allowed for thirty six keys per octave (over the three keyboards) – this meant that instead of the usual black and white key layout, the manual consisted of alternate black and white keys and the player had to learn to play over three manuals to achieve an equal tempered scale. Despite this nightmarish keyboard-complexity the Telharmonium had the unique ability – if required – to play over a variety of intonations.

A unique clutch like device allowed the player to control expression using key velocity as well as with a foot pedal. The resulting sound was fed through the wire network and streamed to the audience through large, six-foot acoustic horns of various designs– Cahill experimented with numerous horn designs using different thicknesses of wood, metal carbon and paper to acquire the right range of tones.

For the Telharmonium to be audible beyond a telephone receiver it needed a much more current than the standard telephone; the output power from the Telharmonium’s alternators was as much as 15,000 watts and around 1 amp at the receiver – compared to a telephone receiver designed for currents as low as six ten-trillionths of an amp. This power did allow the Telharmonium to be audible to an audience but caused interference with the New York telephone network and needed a huge amount of electricity to keep it running.

The sound of the Telharmonium

The first description of the sound of the Telharmonium was from Ray Stannard Baker writing for McClure’s magazine describing a demonstration of the Washington MkI Telharmonium at the Hotel Hamilton;

“The first impression the music makes upon the listener is its singular difference from any music ever heard before : in the fullness, roundness, completeness, of its tones. And truly it is different and more perfect: but strangely enough, while it possesses ranges of tones all its own, it can be made to imitate closely other musical instruments: the flute, oboe, bugle, French horn and ‘cello best of all, the piano and violin not as yet so perfectly. Ask the players for fife music and they play Dixie for you with the squealing of the pipes deceptively perfect. Indeed, the performer upon this marvelous machine, as I shall explain later, can “build up” any sort of tone he wishes : he can produce the perfect note of the flute or the imperfect note of the piano — though the present machine is not adapted to the production of all sorts of music, as future and more extensive machines may be. After several selections had been given I was conscious of a subtle change in the music. Dr. Cahill said: “Mr. Harris has taken Mr. Pierce’s place.” It is quite as possible, indeed, to distinguish the individuality of the players upon this instrument as it is upon the piano or violin. The machine responds perfectly to the skill and emotion of the player; he gets out of it what he puts into it: so that the music is as much a human production as though the player performed upon a piano. In an hour’s time we had many selections, varying all the way from Bach and Schubert to the ” Arkansas Traveler ” and a popular Stein song. One duet was played by Mr. Pierce and Mr. Schultz. The present machine is best adapted to the higher class of music. It does not produce with any great success the rattlebang of rag-time which is perhaps an advantage”

Ray Stannard Baker writing in McClure’s Magazine. 1903

And Thomas Commerford Martin writing in the Outlook on the 5 May ;

“A skillful performer upon the telharmonium can make it blare like a trumpet, snarl like a bassoon, warble like a flute, or sing like a violin. Four or five performers, playing in concert, will ultimately be able, it is believed, to produce an effect closely approaching that of a full orchestra ; for each bank of keys is furnished with a set of stops somewhat like those of an organ, by means of which it can be made to produce tones almost if not quite identical with those of any family of instruments. At one keyboard one player can play the part of the strings ; at another a second player can reproduce the tones of the oboe family ; at another a third player can reproduce the tones of the brass ; and so on. And each player is able in an instant to modify or transform the quality of tone which he is producing. Of course there are limitations in this power to imitate instruments. In the violin tone on the telharmonium there is nothing of resin and catgut ; in the tone of the French horn there is not the occasional break characteristic of that instrument. On the other hand, the quality of tone in the telharmonium is capable of infinite variation.- Instrumental effects are possible on it which have never before been heard.”

Established at the Telharmonic Hall Cahill’s New York Electric Music Co. put on several seasons of Telharmonic music from 1906 – including guided tours of the basement machinery. The repertoire consisted of popular light classical works that emphasised the instrument’s range and flexibility. The audience listed to the music using a variety of horns and speakers including music fed into a series of carbon arc lamps that oscillated with the electronic signal giving an audio and light show (this phenomena had been explored by the British physicist William Duddell and was used in his ‘Singing Arc’ instrument of 1899)

Ray Stannard Baker in McClure’s magazine in 1903 also contemplated the effect the Telharmonium would have on music and the listener arguing that it would ‘democratise’ music:

“As the machine is developed, and as the players become more expert, we may enter upon quite a new era of music, what ma)’ be called, indeed, the democracy of music. We cannot really herald the complete dominance of democracy until we have good music, great pictures, and the best books at the command of every citizen. Museums, galleries, and process printing have gone far towards bringing that equal opportunity of all citizens for the enjoyment of great pictures, which is the dream of the social philosopher. Free libraries have placed the best and rarest books at the command of any man who wishes to use them. But music, by its nature ephemeral and costly of production, has not so easily submitted itself to such democracy of enjoyment. Poor music may be had anywhere: good music is it is hived up in grand opera houses, and supported by playing upon the social vanity of the rich. It is a pastime for society. To this fact, indeed, may be traced the slow development, much deplored by critics, of musical taste in this country.”

The Three Telharmoniums

In all Cahill designed and built three versions of the Telharmonium (with five patents);

The, MkI version, as described in his 1897 patent, Cahill built by hand in his laboratory in Washington and, weighing a mere 14,000lbs was essentially a working prototype designed to raise capital for a planned full version .

Once enough interest had been generated to finance the development of the Telharmonium Cahill and his associated moved to the Cabot St Mill in Holyoke, Mass. where construction of the much larger MkII commenced in 1902. the MkII was constructed by a workforce of fifty engineers, grinders, reamers, assemblers and other workers under the guidance of Cahill.

The MkII consisted of eight 11” steel shafts bearing a total of 145 alternators. The 60-foot mainframe was built of 18” steel girders set on brick foundations. Ten switchboard panels contained almost 2,000 switches. The whole apparatus weighed 200 tons and cost $200,000 and assumed the proportions and appearance of a power station generator.

It was this version that was disassembled in 1906 and transported to by railroad to be installed at the ‘Telharmonic hall’ on 39th Street and Broadway New York City where it was previewed to an audience of nine hundred people. The MkII Telharmonium remained in NYC for another four years giving regular concerts and ‘broadcasts’ at the Telharmonic Hall and other fashionable venues across the city. Despite it’s initial success the subscriber business foundered after the 1907 financial panic and Telharmonic Hall closed in 1910.

After the collapse of the ‘Telharmonic Hall’ business, Cahill regained control of the rights to his invention and stoically rebuilt and refined the design to create the final MkIII version back at the Cabot St mill. The Mk III, again weighing 200 tons but with a number of significant improvements including new alternator designs and a standard keyboard for a tempered scale, was installed in the basement of a building on west 56th st NYC. It was here that the Telharmonium made it’s final debut in Feb 1912 streaming music to the Chapter room of Carnegie Hall. Despite Cahill’s improvements and tireless promotion of the instrument, ‘Telharmony’ had lost the novelty value that sustained public interest six years previously and subscribers failed to materialise. Cahill finally filed for bankruptcy in 1914. The MkII and III Telharmoniums were sold for scrap. The remains of the first Telharmonium were kept by Cahill’s brother Arthur but were also scrapped after his death in 1958.

THE TELHARMONIUM – AN APPARATUS FOR THE ELECTRICAL GENERATION AND TRANSMISSION OF MUSIC. Dr. Thaddeus Cahill’s system of generating music at a central station in the form of electrical oscillations, and of transmitting these oscillations by means of wires to any desired point, where they are rendered audible by means of an ordinary telephone receiver or a speaking arc, is now embodied in a working plant situated in the heart of New York. Although this apparatus constitutes b.ut a portion of a plant that may ultimately assume very remarkable dimensions, and although it has limitations imposed by its size, the results obtained are so promising, that many applications have been made by prospective subscribers for connection with the central station. When a larger number of · generators and keyboards is installed, as they doubtless will be in due time, there is no reason why the telharmonium, as the invention is called, should not give the subscribers all the pleasures of a full symphony orchestra whenever they wish to enjoy them. At present ‘ very beautiful effects are secured on a . less elaborate scale, but in eveI\ly way comparable with those of a good quintet.. And several additional keyboards now in building at Dr. Cahill’s works at Holyoke, Mass., where the New York plant was built, are nearing completion, and will probably be in service at Broadway and Thirty-ninth Street in the course of another month or two. Perhaps the feature which most astonishes the technically Uninformed man when Dr. Cahill’s invention is first exhibited to him is the fact that music in the ordinary sense of the word, in other words, rhythmic vibrations of the air, is not produced at the central station. The vibrant notes of the flute, mingled with the clarinet or viol-like tones which are heard at the receiving end of the wire, spring from no musical instrument whatever. Nowhere is anything like a telephone transmitter used, although the electrical oscillations which are sent to the receiver and there translated into audible vibrations are quite like those set up in an ordinary telephone circuit, except that they are enormously more powerful. Briefly summed up, Dr. Cahill’s wonderful invention consists in generating electrical oscillations corresponding in period with the acoustic vibrations of the various elemental tones desired, in synthesizing from th ese electrical vibrations the different notes and chords required, and in rendering the sYnthesized electrical vibrations audible by a translating device. In the New York plant the electrical vibrations are produced by 144 alternating dynamos of the inductor type, having frequencies that vary from 40 to 4,000 cycles. These alternators are arranged in eight sections or panels, each inductor being mounted on an ll-inch steel shaft. One inductor dynamo is used for each note of the musical scale, each generator producing as many electrical vibrations per second as there are aerial vibrations in that note of the musical scale for which it stands. The fixed or stator part of each dynamo carries both the field and armature windings ; the rotors are carried on shafts geared together, the number of teeth ( pole pieces) on the gear wheels corresponding with the number of frequencies to be ob-. tained. Because the rotors are geared together, the frequencies are fixed and tuning is unnecessary. The alternators are controlled each by a key in a keyboard upon which the musician plays. Each key serves to make and break the main eircuit from seven alternators, not directly, but through the medium of plunger relay magnets wound with layers of enameled wire. Only feeble and harmless currents are needed to control the relay magnets, by which the task of making and breaking the currents from the main circuits is r’eally performed. No appreciable ‘ time elapses between the depression of a key and the closing of a main alternating circuit, so that the keyboard is as responsive and sensitive as that of a piano. The elemental notes generated by the . 144 dynamos cannot alone be used to produce the most pleasing musical effects. Why this should be so becomes apparent from a consideration of some Simple principles in acoustics. If a wire be stretched between two points A and B (see the accompanying diagram) and plucked or struck, it will vibrate above and below the line A, B and give what is known as a fundamental tone. This fundamental tone is without distinctive musical character or timbre, and would sound the same in all instruments, so that one could not distinguish whether it came from a violin or a piano. In addition to its fundamental vibration between its pOints of attachment, the string undergoes a series of sub-vibrations above and below its own normal curve, which it will pass at certain points, nodes, dividi????g it into equal parts. Thus in the accompanying sketch, A, 0, B and A, D, B represent the fundamental Vibrations, and A, E, 0, F, B, the first sub-vibration intersecting the fundamental vibration at the node 0. Again, the string may vibrate in three parts, four parts, five parts, etc. The effect of the sub-vibrations is added to the effect of the fundamental vibration, and their total effect is heard in the distinctive quality or “tone Color,” as it is called, of the particular instrument played. The sub-vibrations are known as the upper partials or overtones, and generally speaking, they are harmonious with one another and with the fundamental tone. That very elusive and uncertain quality called timbre is dependent entirely upon these overtones. By properly controlling the blending of the overtones and the elemental tones, it ought to be possible to. imitate the characteristic timbre of any musical instrument. This Dr. Cahill has in a large measure succeeded in accomplishing. “Tone mixing,” as this building up of harmonious notes and chords is called, is effected in the telharmonium by superposing the simple or sinusoidal waves of the alternators. By means of bus-bars the oscillations of the ground tones are all brought together in one circuit, those of the first partials in another circuit, those of the second partials in a third circuit, etc. The actual blending is done by passing the various oscillations through a series of transformers. In order to understand how a chord is blended, we must begin at the keyboard. As soon as the performer depresses his keys, the bus-bars electrically superpose the ground tone currents , through the primaries of closed-iron magnetic circuit transformers, the secondaries of which are jained in circuit with impedance rheostats governing the strength of the currents, which rheostats are controlled from the keyboard by means of stops. Similarly the bus-bars superpose the first, second, third, and other desired partials in separate circuits. The composite ground-tone a’nd overtone oscillations thus produced in the secondaries of the transformers are next passed through the primaries of an open-iron magnetic circuit transformer, in the secondary circuit of which a current is produced composed of all the ground tone and overtone frequencies of the particular chord under consideration. This secondary current is in turn passed through the primary of an air-core transformer, and the resultant secondary current is converted by telephone receivers or speaking arcs into the musical chord desired. In order to listen to this musical chord, the telephone receiver is not held to the ear. It would be bad for the ear if it were, when a loud note is sounded. The current of the receiver is literally thousands, and at times millions of times stronger, measured in watts, than those to which an ordinary telephone receiver responds. Whereas less than six tenmillionths of an ampere are sufficient to produce a response from an ordinary telephone receiver, a current of an ampere is sometimes used in the Cahill system for an instant when loud tones are produced. The composition or quality of a note or chord is controlled by eight rheostats called stops. By skillful manipulation of the stop rheostats, it is possible to obtain very accurate imitations of the wood-winds and several other orchestral instruments. Imitation, however, is hardly the right word ; for the notes are built up of exactly the same components as the tones which come from the reaJ instruments. Furthermore, beautiful effects are obtained that cannot be produced on any existing instrument. These stop rheostats control merely the timbre or quality of the music produced. Fluctuations in volume are produced by “expression rheostats.” Both stop and expression rheostats are constituted by impedance coils, differing however in mechanical construction. The stop rheostats are manipulated very much like the stops of an organ, and the expression rheostats like the swell. Unlike an organ swell, however, the expression rheostats are used not only for producing captivating crescendos and diminuendos of individual notes and chords, but also in reproducing the peculiar singing tremolo of the violin and ‘cello. The rather complex system of transformers described serves not merely to blend partials with ground tones, but also to purify the vibrations corresponding with the different sets of partials by purging them of their harsher components. The air core transformers, fur thermore, permit the selection of voltages according to the resistance which the final current will encounter. Inasmuch as each keyboard controls ground-tone and overtone mixing devices, it is possible to produce notes of the same timbre or of different timbres. Excellent orchestral effects can, therefore, be obtained by causing the one keyboard to sound wind instruments, such as oboes, flutes, clarinets, or horns, and the other to sound the tones of the violin or other stringed instruments. From this necessarily cursory consideration of the telharmonium, it is evident that the music is initiated as electrical vibrations, distributed in the form of electricity, and finally converted into aerial vibrations at a thousand different places separated hundreds of miles, it may be. No musical instruments in the sense in which we understand the word are used. Not a string, reed, or pipe is anywhere to be found. The vibrations produced by the performers’ playing are wholly electrical, and not until they reach the telephone receiver can they be heard. The telephone reo ceiver acts for us as a kind of electrical ear to hear oscillations to which our own ears are insensitive. When Mark Twain heard the telharmonium, he fancifully suggested that the military parade’ of the future would be a more beautifully rhythmic procession than our present pageants. The usual military bands heading the various regiments and playing marches, not in unison, although the same in time, will give place to musical arcs disposed along the line of march, all crashing out their stntins in perfect time. The soldiers who will march in that future parade win all hear the blare of invisible electrical trumpets and horns at the same moment; they will all raise their left feet at exactly the same instant, just as if they were but one company. So far as the capabilities of the telharmonium are concerned, it may be stated that the New York installation is able to supply ten thousan-d subscribers, or more, with music of moderate volume at widely remote places. The very remarkable and rapid development of the invention has been thus eloquently set forth by Prof. A. S. McAllister in an article published in the Electrical World : “From Hero, who first proposed to utilize the motive power of steam, to Watt’s first successful engine, was almost two thousand years. And between the proposal of Hero and the accGmplishment of Watt many inventors in different countries made ineffective attempts to attain the goal desired. From Huyghens’s proposal of an explosive motor to Otto’s successful machine two centuries elapsed, with scores of patents in the different countries of Europe. So from Sir Humphry Davy’s experimental arc to the Brush and Edison arc lighting machines” three-quarters of a century elapsed, during which scores of inventors in different countries endeavored to solve the problem in vain. Similar remarks apply to the progress of most great inventions, electri· cal and mechanical. But the process of producing music from dynamos has been carried from the first conception to the successful working machine by one man-Thaddeus Cahill-in a few years. And when one hears the plant at Thirty-ninth Street and Broadway, with its musical tones already equaling, if not surpassing, the instruments of the orchestra, one wonders what cannot be expected in a few years to come when the inventor will have had time to do his best, and when his work in all its details will be known ·to the world and open to improvement by others, and when musicians will have learned to use the new powers which electricity is placing at their command. Clearly the world has, through the wonderful powers of the electrical forces and the skillful use made of them by Dr. Cahill, a new music, a music which can be produced in many thousand places simultaneously, and which in its very infancy seems destined to surpass in sympathy and responsiveness-in artistic worth-the existing music of pipe and string, the evolution of many centuries.”

From ‘Scientific American’ vol 96 #10 9th March 1907

The end of the Telharmonium

The reason for the failure of Cahill’s project were numerous. The machine itself was impossibly expensive; about $1 million was spent from 1897 to 1914 on the project ( approximately $30 million in today’s value) and it was unlikely that a subscriber business model would have ever covered the costs, let alone make a profit – and, even if Cahill had found enough subscribers, he’d have to have built a power plant to generate enough power.

The output power of the Telharmonium caused great disruption of the New York Telephone network, angering telephone subscribers and even interrupting the Stock Exchange, which resulted eventually in AT&T refusing to co-operate in supporting Cahill’s instrument.

The Telharmonium was also a victim of an age of rapid technical advances; Lee De Forest began experimenting with radio transmissions as early as 1906 (which included transmissions of the Telharmonium) and by around 1914 wireless radio broadcasts had spelled the end for wire broadcasting.

The technology developed by Cahill did however continue. In 1934 the American watchmaker Laurens Hammond developed a new electronic home organ which was essentially a miniaturised Telharmonium

“Thaddeus Cahill, developer of the Telharmonium, was . . . endowed with the ability to think big. Although not strictly electronic (it predated the invention of the vacuum tube by about a decade), the Telharmonium embodied many basic principles that have been used in the electronic music medium: the generation of pitched tones from alternating electricity, the addition of harmonics to determine tone color (additive synthe- sis), and a touch sensitive keyboard to shape the sounds and control their strengths. This first polyphonic, touch sensitive music synthesizer remained in service in New York for only a few years . . . The basic idea was resurrected again in the 1930s in an instrument that was somewhat more of a commercial success: the Hammond Organ.”

Robert A. Moog,”ElectronicMusic,”Journal of the Audio Engineering Society, October/November 1977, 25:10/11, 856.