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To understand a little bit of the excitement and technical facilities and problems of electronic music it’s necessary to delve in the technical stuff.

Sound itself is a vibration of air; it is a change of the air pressure. The vibration can be heard through the mechanism of our ears. The vibrations have frequencies and that is measured in Herz. The average human ear can hear sounds between 20 en 20.000 Hz, whereby 20 is very low and deep and the 20.000 is an almost inaudible high screech.
Sound is mostly made visible in a wave-form (sinus). The length of the waves (amplitude) gives you the clue to the sound volume; the width of the waves: the pitch.
Sound travels through various mediums (air, water, etc.) but not through a vacuum space. In a normal room sound travels with a speed at 343 meters/second.
The loudness of the produced sound can give the receiver (the ear) a clue about distance and/or the motion of it if it is moving (planes, trains, etc.). The closer the louder. Very soft sounds cannot be heard, but of course you can create a louder sound by amplifying it. The loudness of sounds is measured in decibels - dB (which comes from Alexander Graham Bell – the inventor of the telephone). A normal conversation is on average 60 dB, a car 80 and so forth. Around 130-140 dB is the so called pain threshold. At this level sound is experienced as pain. You can damage your ear permanently by frequently exposing your ears to loud sounds. Some sounds are heard as well felt, because of the airpressure.

All music is made of sounds. By manipulating sounds you can create music. Electronic music mostly uses sounds created in an electronic way. That sounds simple, but it isn’t. The first attempt to create electronic music was by using a telephone station (see page one on this site). Creative minds build machines to give them the sounds they could hear in their heads. But sometimes it was impossible, because of the lack of facilities. The first sound machines like the Theremin and Ondes Martenot gave sounds, but not the new world of sound people were searching for. Mostly the older electronic music now sounds very outdated and normal, not even strange.

Maybe Edgard Varèse was the most important figure searching for new sounds. He would abandon the old world of sounds created by symphony orchestras. In the new world, guided by the ongoing industrial revolution, he thought, there was no place for the limitations in sounds. “Away with the violins, enter the drums = noise and electronics!” He never said it precisely in this way, but it was his aim when creating music. He used sirens and other new sounds in his music.
The first real step into the future of sound was with the invention of the tape-recorder. The first practical tape recorder came from Germany in 1935 and was developed by AEG: the Magnetophon K1. Friedrich Matthias of IG Farben/BASF developed the recording tape made of (oxide, binder, and backing material).
It was the starting point for many composers, to use the tape and the tape-recorder as music machine, not only because they could record their own sounds, but because tapes could be manipulated by slowing them down or speeding them up or even reversing them. You could create loops (tape looped together with special tape and simply played through the recorder with forever repeating sound). Tape loops could have length of more than 1 meter. Even more exciting you could cut the tape (splicing) and put together in different ways. It gave the composer a new tool for their creativity.

Musique Concrète
After the recorder was introduced in electronic music there was another view towards music coming from France. Pierre Schaeffer started using every day sounds to create his music. Often the sounds were electronically manipulated. His point was that people would appreciate electronic music more if it made use of realistic, or well known or recognizable sounds. Well… the sounds were also cut, chopped up on tapes, reversed, slowed down, and speeded up. It worked, but not for long because there were always new ways appearing to create sounds.

Oscillators / tone generators
One of the earliest pure electronic sounds was made with the help of oscillators. An oscillator is an electronic circuit that gives a specific signal. This could be continuous or repetitive. Oscillators are used in radios, televisions, clock signals and various kinds of sounds, but also in synthesizers. The signal or sound that it produces is the so called sine waves,  or square waves.
A variation, created with a more advanced oscillator, is the saw tooth wave. It is rich in harmonics and is so named because of the visual signal looks like the tooth of a saw, whereas the sine wave has more of an up-and-down waveform.

Early synthesizer
If you combine a varied set of oscillators or tone generators in one machine and also  have the possibility to adjust sound, pitch, attack, duration and decay as well as being able to generate, modify, process and record you come near the early form of a synthesizer. The first form of such a machine was the Olson-Belar Sound Synthesizer (1955), later named RCA Electronic Music Synthesizer. RCA rented their first synthesizer to the Columbia Princeton Electronic Music Center. In 1959 they gave their Mark II version on a kind of permanent lone base. The instrument attracted many composers to the Music Center and it was frequently used.

More components
With the increasing technical facilities new additions were developed. Important for electronic music was the VCO: voltage controlled oscillator. The VCO
is an electronic oscillator designed to be controlled in oscillation frequency by a voltage input. The more voltage, the more rapid the vibrations and the higher frequency. In addition also a voltage controlled amplifier was built. One of the people who helped build the VCO was Robert Moog, later known as the inventor of the Moog Synthesizers.

and more…
Around 1953 the first multitrack tape recorder was invented by Raymond Scott. He patented machines which could record seven and fourteen tracks on one single reel. The same Raymond Scott invented another electro-mechanical device: the sequencer. His sequencers could produce rhythmically uniform parts (sequences). Many years later more sophisticated sequencers were used as the rhythm foundation for electronic groups like Tangerine Dream. In 1955 Hugh Le Caine build the SPTR - the Special Purpose Tape Recorder, a multi tape playback instrument, a precursor of the sampler. It had six tapes which could be synchronized for playback.
Uo until this point most keyboards didn’t function as a piano. Hugh Le Caine invented the touch sensitive organ (1952). It was a very significant step forward in the development of synthesizers.
The first synthesizers were all monofic (one note at the time). Only in 1970 the first polyphonic machine was built, again by Le Caine, who was very dedicated to his machines. 

sound made visible

Tri-Ergon optical sound recording 1922

an original magnetophone from AEG

Dick Mills (left) and John Harrison with tape loop

Dr. Harry P. Olson at the keyboard
and Herbert Belar at the control panel
of their Sound Synthesizer

Robert Moog

Hugh Le Caine