It can't emphasized enough, the impact the cinema process Cinerama (early 50s) had on influencing not only the movie industry, but also the way the public and the recording industry viewed the concept of 360 degree surround sound. The Cinerama process which was totally unique at time with its huge, wrap-around, deeply curved screen and 7 channel, 360 degree sound was hugely popular with the public. The first film made in this process, THIS IS CINERAMA, and the subsequent releases ran with sold-out shows for months. The whole concept of an immersive visual and aural experience thrilled audiences. It also electrified the Hollywood studios (Cinerama did not come from any of the big Hollywood studios, but from visionary, independent entrepraneurs). The big studios saw the lines around the block to someone else's film and they wanted in on it. Darryl Zanuck, head of 20th Century Fox, set his engineers to mimic Cinerama and thus CinemaScope with its wide screen and multi-channel sound was born with THE ROBE (1953). He insisted the CinemaScope system include stereo sound and with a surround channel just like Cinerama. Both those systems had discrete, magnetic sound. What these motion picture systems also had in common was that sound now wrapped around the listener to create an immersive, aural experience. Both Cinerama and then CinemaScope's surround channel insured that surround sound would remained the goal of any cinema playback system from then on. Quadraphonic sound in the 70s was the first attempt to bring that cinema experience which was so popular with the public, into the home.
The result was the matrix encoding system that allowed the four channels of sound to be recorded/played back with only two channels avaliable on the LP disc. The beauty of the matrixed system -- the LP quad system that survived the competing non-matrix system -- was that even though it was designed to playback records that were specifically recorded with 4 channels of mextixed quad sound, any LP play with the matrix decoder engaged, would route all of the out-of-phase audio that naturally occurs in a recording session, to the rear channels. That material is almost always the ambience of the room and the reflected sounds off the room walls. It with it playing back from the rear channels, it is a much more immersive sound for the listener than the same LP played back in only 2 channels. Many who had installed a decent quadraphonic system in the 70, never removed it, even after the quad encoded LPs were no longer produced. Any stereo source played thru the matrixed quad system was enhanced with an added, much broader surround-sound quality.
Factoid -- even when Dolby stereo was introduced to cinemas, the Dolby Stereo system was really just a modification of the Sansui Type II quadraphonic matrix system. That is the way Dolby was able record multi-channel surround sound onto only the two audio channels available on the optical film soundtrack (just as the Quad systems of the 70s was able to record 4 channels of sound onto only 2 groove tracks of the LP. Instead of using two channels of surround with one channel for each corner of the room, Dolby only used a single surround channel, so in a sence, the orginal quadraphonic matrix system of the 70s was a more sophistocated system than the Dolby cinema system with its single surround channel. Also, the Dolby cinema system required that the single surround channel's high end incorporated a cut-off at 8KHz (hardly high fidelity); whereas no such limitation was placed on the consumer quad system which had two full-range surrounds.