Thaddeus Cahill and his Telharmonium:                    

In 1897 Thaddeus Cahill patented  his invention the "Telharmonium" or "Dynamophone," which is considered  the one offirst significant electronic musical instrument . The first fully completed model was presented to the public in 1906 in Holyoke, Mass.

The Telharmonium was essentially a collection of 145 modified dynamos using  a number of specially geared shafts
and associated inductors to produce alternating currents of different audio frequencies. These signals were controlled by a multiple set of keyboards of seven octaves and banks of controls.     The instrument was usually played by two musicians.  

The first model, which was a huge structure weighing 200 tons and was 60 feet long, used acoustic horns built from piano soundboards however later on models were linked directly to the telephone network.  Using the telephone network was the only way to amplify the sound, since amplifiers had not yet been invented.  The Telharmonium supplied 1 amp of power to each telephone receiver on the network, however later on over the years, he realized that using the telephone receivers did cause interference with telephone calls. 

In this picture of the Telharmonium, you can see that the instrument is monstrous.  At an estimated cost of $200,000, this instrument took up entire floor of "Telharmonic Hall" on 39th Street and Broadway New York City for 20 years!  You can see that it would be an amazing feat to move this instrument, however it was done.  Using 30 railroad cars, it was transported from Holyoke, Mass to NYC.  

Why do we not see this instrument around today?
Although Cahill's ideas were far ahead of his time musically, the instrument was unpopular because musicains had to take the time to learn and practice on the unusual keyboard.  The sound produced from the Telharmonium at Telharmonic Hall, was many times filled with cable trasmission interferneces and as sudden drops in volume, which led to a 'highly irritating' concert.  Although Cahill and the 'New England Electric Music Company' had a wonderful vision of installed the Telharmonium in hotels, restaurants, and private home using the telephone network, however it proved to be a failure because of the interference with telephone calls.   The Telharmonium operated until 1916, but became obsolete due to popular radio broadcasting and amplification.  Unfortunatly there are no recordings of the instrument, but many of the same principles still are seen in the Hammond organ.

It is important to note that the Telharmonium did trigger the beginning of electronic music.  The Italian Composer Ferruccio Busoni inspired by the machine wrote his "Sketch of a New Aesthetic of Music" (1907) which became the  inspiration for a new generation of electronic composers such as Edgard Varèse and Luigi Rusolo .

Lev Sergeivitch Termen & "The Theremin" 

The Theremin was built using the principles of beat frequency and vaccum tubes. This effect is created by two high radio frequency sound waves of similar but varying frequency combining and creating a lower audible frequency, equal to the difference between the two radio frequencies (approximately 20 Hz to 20,000 Hz). The musical potential of the effect was noted by several engineers and designers including Maurice Martenot, Nikolay Obukhov, Armand Givelet and Leon (or Lev) Sergeivitch Termen, the Russian Cellist and electronic engineer.   The useage of the vacuum tube oscillator became the standred way of producing electornic sound.