in this country under Ralph J. Oace. Then in 1945 the signal corps captain John Mullin found Magnetophones at Radio Frankfurt in Germany and 1000-meeter reels of 6.5mm ferric-coated BASF tape with 20-min. capacity: he mailed 2 machines to the united states with 50 reels of tape, and after the war worked on them to improve the electronics. The next year, 1946, Mullin demonstrated Magnetophones at San Francisco Institute of Radio Engineers on may 16, and Harold Lindsay told Ampex boss Alexander M. Poniatoff who began work on developing a united states-made magnetic tape recorder. Then in 1947 Mullin introduced the magnetophones to Bing Crosby Enterprises in June. Then in 1948 the first U.S.-made Ampex Model 200 tape recorder. Also the 3M scotch 111-gamma ferric oxide coated acetate tape. In an other view, in 1948 Columbia introduced the first 12-inch 33-1/3 rpm micro-groove LP vinylite record with 23-minutes per side by Peter Goldmark. Then in 1949, RCA Victor introduced 7-inch 45rpm micro-groove extended play vinylite record and player. Also in the rock and roll, Todd Storz of Omaha's KOWH created Top 40 after observing customers in bars play the same juke box selection over and over.
             In the 1950's, there were also many inventions like Muddy Waters recorded rollin' stones for the Aristocrat label of Leonard and Phil Chess on Chicago. Also Sam Philips recorded the rocket 88 with his Ampex 350 tape machine. In 1953 Elvis Presley in the simmer made his first recording. Also the "slapback" audio was created. Then, Bill Haley recorded the rhythmic Shake, Rattle and rock and roll around the clock on Decca. Also E
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