In 1947, the producer for Bing Crosby's popular radio show, Murdo MacKenzie, thought that he would have to have the announcer, Ken Carpenter, re-do a certain commercial, because Carpenter had slipped up. Carpenter had said "The new Philcos gives ..." The "s" sound at the end of the verb made the sentence ungrammatical. But then Jack Mullin, who worked the Crosby show's tape machine, had a revelation. He snipped off that "s" sound and re-spliced the tape, so that anyone listening to the broadcast would "hear" Carpenter say, "The new Philcos give ... " This was something new. As Greg Milner has written, recording technology in 1947 took the huge step from merely archiving reality to faking it.
The radio world soon build on Mullin's revelation. One can do a lot more with the magnetic tapes then ubiquitous in recording than just cutting out mistakes. One can loop a tape, for example, slicing one end to another so a phrase or tune repeats itself as often as is desired. Or, one might want to develop an "echo," a single sound that will repeat itself but in a weakened and fading form. This can be accomplished by allowing the output of a tape to feed back into the input.
Echo effects, sometimes called "leak back," became part of the history of rock and roll, especially at Sun Records in the mid 1950s. Milner quotes Jack Clement, an engineer at Sun Records, saying, "Sound would leak back into the vocal mike, and for some reason that sounded good." Clement persuaded the owner of Sun, Sam Phillips, to buy a submixer, so he could apply echo effects selectively -- to some elements in the music rather than others.
But the product that Sun Records and other studios were selling wasn't a magnetic tape, or a broadcast performance. It was a vinyl disc. In the late 1940s, RCA had introduced a disc designed to revolve 45 times per minute (rpms). The 45 became the dominant means for purchasing and listening to "singles" throughout the 1950s, replacing the older 78 rpm record.
The Beatles were a driving force in the development of audio technology through the 1960s, such as the use of four tracks, and eventually more, in the studio. But the use of what they called STEED -- single tape echo and echo delay -- in the song "Everybody's Trying to be My Baby," (1964), which is the technique that makes George Harrison's voice reverberate impressively, shows the continued viability of the effects pioneered under Sam Phillips years before.