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  Wax cylinders are also in use as a recording media
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  Valdemar Poulsen
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  Were commonly used. Far supperior to anything before.
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  Fantasia was the first film to use stereo sound.
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  Analog, with preemphasis and other equalization techniques (LP, RIAA); lateral grooves, horizontal stylus motion; discs at 7" , 10" and 12"
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  In the 1940's Ampex started to sell personal tape recorders. From the 1950's throughout to the 1980's, tape was the standard medium used for recording.
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  Became more popular in the late 60's early 70's when improved recording was made. Most popular in the 80's.
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  Les paul uses the first 8-track tape recorder to create multi-track recordings (Although 4-track tape recorders were still in common use through the 1960s)
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  Invented by Ray Dolby
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  Then called Sound Designer
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  Legal digital downloads became widely available with the debut of the itunes store