To hear music before Edison, you either had to know how to play an instrument or go to a concert. The Gramophone brought music home, as did the radio, but the sound quality was nothing like a concert experience. After WWII, quality music reproduction became the province of the home hobbyist, thanks to the development of high-fidelity stereophonic recording and playback, otherwise known as hi-fi.

Hi-fi was actually the convergence of several technologies. The first was the concept of stereo sound from multiple speakers that simulated a live performance. The first patents for "binaural", or stereophonic recording and reproduction, were applied for in 1931 (awarded in 1933) to British engineer Alan Blumlein. At the same time, Bell Labs researcher Arthur C. Keller was developing binaural recordings using two styli cutting twin tracks on the same wax records. In 1933, the first stereo "broadcast" was made of a concert in Philadelphia piped to Washington, D.C., by telephone.

But recording, playback and broadcast technology at the time was ill-equipped to handle true stereo signals. The transistor, which created more efficient signal amplification, was the second breakthrough on the road to hi-fi. Next was the refinement of the physical playback media – magnetic tape and vinyl records.

In 1888, Oberlin Smith authored a scientific journal article describing a method of magnetic sound recording presaging today's audiotape. In 1893, Danish inventor Valdemar Poulson magnetized steel cable to create wire recording, the predominant audio recording technology for the next 40 years. Between 1932 and 1935, the German industrial giant I.G. Farben AG developed the first magnetic tape recorder, the Magnetophon. The machine was co-developed by Farben and the German General Electric (AEG), and then manufactured by Telefunken. By 1935 Adolf Hitler was using magnetic tape to record and broadcast speeches, unbeknownst to western engineers. In between, in 1939, Marvin Camras of Armour Research invented a wire recorder that was used by the military throughout World War II.

In 1942, the first stereo tape recordings were made by Helmut Kruger for German Radio in Berlin. Army signal corpsmen were befuddled by early morning radio concert performances from Berlin that clearly weren't being broadcast live but just as clearly could not have been recorded because of their high-fidelity sound.

By the end of the war, rumors were pervasive in the American Army Signal Corps that the Germans had developed high-fidelity tape recorders. During the summer of 1945, corpsmen scoured the French and German countryside, acquiring the remnants of the German recording and radio industry. Major John T. Mullin found two Magnetophons and sent them, along with several reels of red oxide tape made by Farben's BASF division, to his San Francisco home and started to tinker.

Back home, Mullin worked with Colonel Richard Ranger, who in 1924 had invented the precursor to the modern fax machine and who, while serving in the Army during World War II, also had discovered the Magnetophon while poking through the ruins of the Third Reich. But each man decided to pursue his own commercialization path.

In May 1946, Mullin presented his rebuilt Magnetophon tape recorder, the first stereo tape recorder in the free world, to the Institute of Radio Engineers. Bing Crosby's engineers quickly hired Mullin and his machine to tape the singer's radio show.

Two years later, a tiny company founded by Russian émigré Alexander Poniatoff called Ampex Corp., with Mullin's help, introduced the Model 200 stereo tape recorder, making high-fidelity stereo recording commercial. 3M, under the Scotch brand name, made the first magnetic recording tape, first paper then acetate-based. Several companies began manufacturing tape recorders by the late 1940s, including Ranger's Rangertone, Magnecord and Brush.