Dolby Surround 7.1 and Dolby Atmos in 2010 and 2012 respectively. Modern home audio and video The progress of stereophonic sound was paced by the technical difficulties of recording and reproducing two or more channels in synchronization with one another, and by the economic and marketing issues of introducing new audio media and equipment. A stereo system cost up to twice as much as a monophonic system, since a stereo system contains two preamplifiers, two amplifiers, and two speaker systems. In addition, the user would need an FM stereo tuner, to upgrade any tape recorder to a stereo model, and to have their phonograph fitted with a stereo cartridge. In the early days it was not clear whether consumers would think the sound was so much better as to be worth twice the price. Stereo experiments on disc Lateral and vertical recording Thomas Edison had been recording in a hill-and-dale or vertically modulated format on his cylinders and discs since 1877, and Berliner had been recording in a side-to-side or 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 where the performer needed to shout or play very loudly into what basically 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 but only in the lateral plane. So, even though with all other factors being equal, the lateral plane of recording on disc had the higher fidelity, it was decided to record vertically to produce higher-fidelity recordings on these new 'silent-surface' materials, for two reasons, the increase in fidelity and the incompatibility with