Source: Electronicmusic.com
In 1874 Elisha Gray discovered that his nephew had built by accident an electric circuit that produced a sound. Gray reproduced the experiment and developed the principle of self-vibrating electromagnetic devices. The first "musical telegraph" or "harmonic telegraph" was equipped with enough tone oscillators to play two octaves. Gray took the instrument on tour with him in 1874.
Cahill is considered the inventor of the first serious musical electronic instrument. His 1896 patent described a device with electrical tone generating devices, dynamics-controlling devices for building tones, a keyboard for activating the tone-generating circuitry, and a loud-speaker. He was able to use the telharmonium to imitate common orchestral instruments like the oboe, cello or violin.
The first large telharmonium was gigantic: it occupied the better part of the factory in which it was located. The entire instrument weighed about 200 tons!
In the year 1900, in London, streetlights generated light using an electric arc which produced an annoying whining sound. William Duddell was trying to devise a way to eliminate this sound and found a way to control its frequency! He attached a keyboard to his first voltage-controlled device and took the instrument on tour. The "Singing Arc" became a novelty by the turn of the century.
This instrument is the invention of the Russian scientist Leon Theremin. It was first built in Russia in 1920 but did not gain an audience until 1928. The technical principle of the theremin is a phenomenon known as heterodyning: when you mix two signals with two slightly different frequencies the resulting signal has a frequency equal to the difference of the two frequencies. Theremin applied this to his instrument by using a reference high frequency oscillator and a variable high frequency oscillator: the resulting low frequency varies as the variable high frequency oscillator varies. The variation of the variable oscillator is due to the of the Theremin player body between two antennae. The Theremin, thanks to its original controllers has survived 70 years of technical evolution: a transistorized version of the Theremin is still available today from Big Briar, Inc.
The sound of the Theremin is known as a source for sound in movies such as "The Day the Earth Stood Still".
The Hammond organ was designed in the thirties. From one point of view, it is a miniature version of the Telharmonium: it weighs 200 kg instead of 200 tons. The sound generators are known as phonic wheels. A "cog" wheel is in front of an electromagnet. As the metallic surface in front of the electromagnet varies, it generates an electricin the wire. This signal is then amplified by triode lamps.
Due to its weight it was and is still used by musicians on tour. The jazz and rock musicicians use this instrument extensively. The commercial success of the Hammond organ is due to its price: is as affordable as a piano but allows the player to play jazz rock at home.
While getting his doctorate in physics in 1963, Robert Moog made money by selling do-it-yourself transistorized theremins. One of his transistorized thereminists was Herbert Deutsch, a composer. Moog and Deutsch met in 1963 at a conference. This led to conversation about the need for new electronic instruments. Moog had his very first prototype built in August 1964. The principle of his prototype was the use of voltage controlled generators and filters.
The Moog allows the performer to create his own sounds by connecting modules with wires and by turning knobs. In 1968 a recording of Bach's music called "Switched On Bach" was performed by Walter (Wendy) Carlos. As a result of this musical success, Moog designed other synthesizers such as the Moog System 55. The most popular of Moog's synthesizers is known as the Minimoog.
Additive synthesis is the most intuitive of synthesis methods: you make a sound by adding elementary sine signals from which frequencies and amplitudes evolve. Beauchamp's additive synthesizer was able to generate six harmonics each with their own amplitude envelope. Furthermore, the phase-shift of the second harmonic was voltage controlled. As every part of this synthesizer was voltage controlled, it was possible to use it with other modules to achieve a composite synthesis method(additive, subtractive and modulation synthesis).