Editing Stereophonic sound (section)

==Stereo experiments on disc==
{{more citations needed section|date=April 2014}}

===Lateral and vertical recording===
[[Thomas Edison]] had been recording in a hill-and-dale (vertically modulated) format on his cylinders and discs since 1877, and [[Berliner Gramophone|Berliner]] had been recording in a side-to-side (lateral) format since shortly thereafter. Each format developed on its own trajectory until the late 1920s when electric recording on disc, utilizing a microphone, surpassed acoustic recording which required a loud performance into what amounted to a megaphone in reverse.

At that time, [[AM radio]] had been around for roughly a decade, and broadcasters were looking for better materials from which to make phonograph records as well as a better format in which to record them to play over the narrow and thus inherently noisy radio channel. As radio had been playing the same shellac discs available to the public, it was found that, even though the playback system was now electric rather than acoustic, the [[surface noise]] on the disc would mask the music after just a few plays.

The development of acetate, bakelite, and vinyl, and the production of radio broadcast transcriptions helped to solve this. Once these considerably quieter compounds were developed, it was discovered that the rubber-idler-wheel-driven turntables of the period had a great deal of low-frequency rumble{{snd}} but only in the lateral plane. So, even though with all other factors being equal, the vertical plane of recording on disc had the higher fidelity, it was decided to record vertically to produce higher-fidelity recordings on these new materials, for two reasons, the increase in fidelity by avoiding the lateral rumble and to create incompatibility with home phonographs which, with their lateral-only playback systems, would only produce silence from a vertically modulated disc.

After {{frac|33|1|3}} RPM recording had been perfected for the movies in 1927, the speed of radio program transcriptions was reduced to match, once again to inhibit playback of the discs on normal home consumer equipment. Even though the stylus size remained the same as consumer records at either {{convert|3|mil|μm}} or {{convert|2.7|mil|μm}}, the disc size was increased from {{convert|12|inch|cm}}  to the same {{convert|16|inch|cm}} as those used in early talking pictures in order to create further incompatibility. Now, not only could the records not be played on home equipment due to incompatible recording format and speed, they would not even fit on the player, which suited the copyright holders.

===Two-channel high fidelity and other experiments===
An experimental format in the 1920s split the signal into two parts, bass and treble, and recording the treble on its own track near the edge of the disc in a lateral format minimizing high-frequency distortion, and recording the bass on its own track in a vertical fashion to minimize rumble. The overhead in this scheme limited the playing time to slightly longer than a single even at {{frac|33|1|3}} RPM on a 12-inch disc.

Another failed experiment in the late 1920s and early '30s involved recording the left channel on one side of the disc and recording the right channel on the other side of the disc. These were manufactured on twin film-company recording lathes which ran in perfect sync with one another, and were capable of counter-clockwise as well as conventional clockwise recording. Each master was run separately through the plating process, lined up to match, and subsequently mounted in a press. The dual-sided stereo disc was then played vertically, first in a system that featured two tonearms on the same post facing one another. The system had trouble keeping the two tonearms in their respective synchronous revolutions.

Five years later, Bell Labs was experimenting with a two-channel lateral-vertical system, where the left channel was recorded laterally and the right channel was recorded vertically, still utilizing a standard 3&nbsp;[[Thousandth of an inch|mil]] 78&nbsp;RPM groove, over three times larger than the modern LP stylus of the late 20th century. In this system all the low-frequency rumble was in the left channel and all the high-frequency distortion was in the right channel. Over a quarter of a century later, it was decided to tilt the recording head 45 degrees off to the right side so that both the low-frequency rumble and high-frequency distortion were shared equally by both channels, producing the 45/45 system we know today.

===Emory Cook===
In 1952, [[Emory Cook]] (1913–2002), who already had become famous by designing new feedback disk-cutter heads to improve sound from tape to vinyl, took the two-channel high-fidelity system described [[#Two-channel high fidelity and other experiments|above]] and developed a ''binaural''<ref group=note>The term "binaural" that Cook used should not be confused with the modern use of the word, where "binaural" is an inner-ear recording using small microphones placed in the ear. Cook used conventional microphones, but used the same word, "binaural", that [[Alan Blumlein]] had used for his experimental stereo records almost 20 years earlier.</ref> record out of it. This consisted of two separate channels cut into two separate groups of grooves running next to each other, one running from the edge of the disc to halfway through and the other starting at the halfway point and ending up towards the label. He used two ''lateral'' grooves with a 500&nbsp;Hz crossover in the inner track to try and compensate for the lower fidelity and high-frequency distortion on the inner track.

Each groove needed its own monophonic needle and cartridge on its own branch of the tonearm, and each needle was connected to a separate amplifier and speaker. This setup was intended to demonstrate Cook's cutter heads at a New York audio fair. It was not intended to promote the ''binaural'' process; but soon afterward, the demand for such recordings and the equipment to play them grew, and Cook's company, Cook Records, began to produce such records commercially. Cook recorded a vast array of sounds, ranging from railroad sounds to thunderstorms. By 1953, Cook had a catalog of about 25 stereo records for sale to [[audiophile]]s.<ref>"[https://books.google.com/books?id=YgoEAAAAMBAJ&pg=PA15 Commercial Binaural Sound Not Far Off]", ''Billboard'', Oct. 24, 1953, p. 15.</ref>