A gramophone record (also phonograph record , or simply record ) is an analogue sound recording medium consisting of a flat disc with an inscribed modulated spiral groove starting near the periphery and ending near the center of the disc. Gramophone records were the primary technology used for personal music reproduction for most of the 20th century. They replaced the phonograph cylinder in the 1900s, and although they were supplanted in popularity in the late 1980s by digital media, they continue to be manufactured and sold.
The terms LP record ( LP , 33 , or 33-1/3 rpm record ), 16 rpm record ( 16 ), 45 rpm record ( 45 ), and 78 rpm record ( 78 ) each refer to specific types of gramophone records. Except for the LP, these type designations refer to their rotational speeds in revolutions per minute (RPM). LPs, 45s, and 16s are usually made of polyvinyl chloride (PVC), and hence may be referred to as vinyl records or simply vinyl .
A sound recording and reproduction device utilizing what were essentially disc records was described by Charles Cros of France in 1877 but never built. In 1878, Thomas Edison independently built the first working phonograph, a tinfoil cylinder machine. He intended it to be used as a voice recording medium, typically for office dictation. The phonograph cylinder dominated the recorded sound market beginning in the 1880s. Lateral-cut disc records were invented by Emile Berliner in 1888 and were used exclusively in toys until 1894, when Berliner began marketing disc records under the Berliner Gramophone label. The Edison "Blue Amberol" cylinder was introduced in 1912, with a longer playing time of around 4 minutes (at 160 rpm) and a more resilient playing surface than its wax predecessor, but the format was doomed due to the difficulty of reproducing recordings. By November 1918 the patents for the manufacture of lateral-cut disc records expired, opening the field for countless companies to produce them, causing disc records to overtake cylinders in popularity. They would dominate the market until the 1980s. Production of Amberol cylinders ceased in the late 1920s.
Early disc records were originally made of various materials including hard rubber. From 1897 onwards, earlier materials were largely replaced by a rather brittle formula of 25% "shellac" (a material obtained from the excretion of a southeast Asian beetle), a filler of a cotton compound similar to manila paper, powdered slate and a small amount of a wax lubricant. The mass production of shellac records began in 1898 in Hanover, Germany. Shellac records were the most common until the 1950s. Unbreakable records, usually of celluloid (an early form of plastic) on a pasteboard base, were made from 1904 onwards, but they suffered from an exceptionally high level of surface noise.
In the 1890s the early recording formats of discs were usually seven inches (nominally 17.5 cm) in diameter. By 1910 the 10-inch (25.4cm) record was by far the most popular standard, holding about three minutes of music or entertainment on a side. From 1903 onwards, 12-inch records (30.5cm) were also commercially sold, mostly of classical music or operatic selections, with four to five minutes of music per side.
Such records were usually sold separately, in plain paper or cardboard sleeves that may have been printed to show producer of the retailer's name and, starting in the 1930's, in collections held in paper sleeves in a cardboard or leather book, similar to a photograph album, and called record albums . Empty record albums were also sold that customers could use to store their records in.
While a 78 rpm record is brittle and relatively easily broken, both the microgroove LP 33â…“ rpm record and the 45 rpm single records are made from vinyl plastic which is flexible and unbreakable in normal use. However, the vinyl records are easier to scratch or gouge. 78s come in a variety of sizes, the most common being 10 inch (25 cm) and 12 inch (30 cm) diameter, and these were originally sold in either paper or card covers, generally with a circular cutout allowing the record label to be seen. The Long-Playing records (LPs) usually come in a paper sleeve within a colour printed card jacket which also provides a track listing. 45 rpm singles and EPs (Extended Play) are of 7 inch (17.5 cm) diameter, the earlier copies being sold in paper covers.
In 1930, RCA Victor launched the first commercially available vinyl long-playing record, marketed as "Program Transcription" discs. These revolutionary discs were designed for playback at 33â…“ rpm and pressed on a 30 cm diameter flexible plastic disc. In Roland Gelatt's book The Fabulous Phonograph , the author notes that RCA Victor's early introduction of a long-play disc was a commercial failure for several reasons including the lack of affordable, reliable consumer playback equipment and consumer wariness during the Great Depression. 
However, vinyl's lower surface noise level than shellac was not forgotten, nor was its durability. In the late 30's, radio commercials and pre-recorded radio programs being sent to disc jockies started being stamped in vinyl, so they would not break in the mail. In the mid-40's, special DJ copies of records started being made of vinyl also, for the same reason. These were all 78 RPM. During and after World War II when shellac supplies were extremely limited, some 78 rpm records were pressed in vinyl instead of shellac (wax), particularly the six-minute 12" (30 cm) 78 rpm records produced by V-Disc for distribution to US troops in World War II. In the 40's, radio transcriptions, which were usually on 16 inch records, but sometimes 12 inch, were always made of vinyl, on 78 RPM.
Beginning in 1939, Columbia Records continued development of this technology. Dr. Peter Goldmark and his staff undertook exhaustive efforts to address problems of recording and playing back narrow grooves and developing an inexpensive, reliable consumer playback system. In 1948, the 12" (30 cm) Long Play (LP) 33â…“ rpm microgroove record album was introduced by the Columbia Record at a dramatic New York press conference. In 1949, RCA Victor released the first 45 RPM single, 7" in diameter, with a large center hole to accommodate an automatic play mechanism on the changer, so a stack of singles would drop down one record at a time automatically after each play.
During the reign of the Communist Party in the former USSR, records were commonly homemade using discarded medical x-rays. These records, nicknamed "Bones", were usually inscribed with illegal copies of popular music banned by the government. They also became a popular means of distribution among Soviet punk bands; in addition to the high cost and low availability of vinyl, punk music was politically suppressed, and publishing outlets were limited.
Earliest rotation speeds varied widely, but between 1900-1925 most records were recorded between 74-82 rpm. In 1925, 78.26 rpm was chosen as the standard because of the introduction of the electrically powered synchronous turntable motor. This motor ran at 3600 rpm with a 46:1 gear ratio which produced 78.26 rpm. In parts of the world that used 50 Hz current, the standard was 77.92 RPM, which was the speed at which a strobe disc with 77 lines would "stand still" in 50 Hz light. Thus these records became known as 78s (or " seventy-eights "). This term did not come into use until after World War II when a need developed to distinguish the 78 from other newer disc record formats, an example of a retronym. Earlier they were just called records , or when there was a need to distinguish them from cylinders, disc records . Standard records was also used, although the same term had also been used earlier for two-minute cylinders.
After World War II, two new competing formats came on to the market and gradually replaced the standard "78": the 33â…“ rpm (often just referred to as the 33 rpm), and the 45 rpm. The 33â…“ rpm LP (for "long play") format was developed by Columbia Records and marketed in 1948. RCA Victor developed the 45 rpm format and marketed it in 1949, in response to Columbia. Both types of new disc used narrower grooves, intended to be played with a smaller stylus - typically 0.001" (25 Âµm) wide, compared to 0.003" (76 Âµm) for a 78 - so the new records were sometimes called Microgroove . In the mid-1950s all record companies agreed to a common recording standard called RIAA equalization. Prior to the establishment of the standard each company used its own preferred standard, requiring discriminating listeners to use preamplifiers with multiple selectable equalization curves.
A number of recordings were pressed at 16â…” RPM, but these were mostly used for radio transcription discs or narrated publications for the blind and visually impaired, and were never widely commercially available.
The older 78 format continued to be mass produced alongside the newer formats into the 1950s, and in a few countries, such as India , into the 1960s. As late as the 1970s, some children's records were released at the 78 rpm speed.
The commercial rivalry between RCA Victor and Columbia Records led to RCA Victor's introduction of what it had intended to be a competing vinyl format, the 7" (175 mm) /45 rpm disc. For a two-year period from 1948 to 1950, record companies and consumers faced uncertainty over which of these formats would ultimately prevail in what was known as the "War of the Speeds". (See also format war )
Eventually the 12" (300 mm) 33â…“ rpm LP prevailed as the predominant format for musical albums, and the 7" (175 mm) 45 rpm disc or "single" established a significant niche for shorter duration discs, typically containing one song on each side. The 45 rpm discs typically emulated the playing time of the former 78 rpm discs, while the LP discs provided up to one half hour of time per side (though typically 15 to 20 minutes). The 45 rpm discs also came in a variety known as Extended play (EP) which achieved up to 25 minutes play at the expense of attenuating (and possibly compressing) the sound to reduce the width required by the groove.
From the mid-1950s through the 1960s, in the US the common home "record player" or "stereo" would typically have had these features: a three- or four-speed player with changer (78, 45, 33â…“, and sometimes 16â…” rpm); a combination cartridge with both 78 and microgroove styluses; and some kind of adapter for playing the 45s with their larger center hole. The large center hole on 45s allows for easier handling by jukebox mechanisms. RCA 45s can also be adapted to the smaller spindle of an LP player with a plastic snap-in insert known as a 'spider'; such inserts were prevalent starting in the 1960s.
Deliberately playing or recording records at the wrong speed was a common amusement. For example, playing the song "I'm on Fire" from Bruce Springsteen's 33â…“ LP at a 45 speed gives the singer a falsetto singing voice that sounds very much like Dolly Parton. Subsequently, playing a 45 rpm recording of Dolly Parton at 33â…“ gives her a voice a husky, almost masculine tone.
Canadian musician Nash the Slash took advantage of this speed/tonal effect with his 1981 12" disc Decomposing , which featured four instrumental tracks that were engineered to play at any speed (with the playing times listed for 33â…“, 45 and 78 rpm playback). Faster playback made the tracks sound like punk rock or power pop, while slower speeds gave the songs a thick, heavy metal effect.
The normal commercial disc is engraved with two sound bearing concentric spiral grooves, one on each side of the disc, running from the outside edge towards the centre. Since the late 1910s, both sides of the record have been used to carry the grooves. The recording is played back by rotating the disc clockwise at a constant rotational speed with a stylus (needle) placed in the groove, converting the vibrations of the stylus into an electric signal (see magnetic cartridge), and sending this signal through an amplifier to loudspeakers.
Structure of a typical record
The majority of records are pressed on black vinyl . The colouring material used to blacken the transparent PVC plastic mix is carbon black, the generic name for the finely divided carbon particles produced by the incomplete burning of a mineral oil based hydrocarbon. Carbon black increases the strength of the disc and renders it opaque.
Some records are pressed on coloured vinyl or with paper pictures embedded in them ("picture discs"). These discs can become collectors' items in some cases. During the 1980s there was a trend for releasing singles on colour vinylâ€” sometimes with large inserts that could be used as posters. This trend has been revived recently and has succeeded in keeping 7" singles a viable format.
Vinyl record standards for the United States follow the guidelines of the Recording Industry Association of America (RIAA).  The inch dimensions are nominal, not precise diameters. The actual dimension of a 12 inch record is 302 mm (11.89 in), for a 10 inch it is 250 mm (9.84 in), and for a 7 inch it is 175 mm (6.89 in).
Records made in other countries are standardized by different organizations, but are very similar in size. The record diameters are typically 300 mm, 250 mm and 175 mm.
There is an area about 6 mm (0.25â€³) wide at the outer edge of the disk, called the lead-in where the groove is widely spaced and silent. This section allows the stylus to be dropped at the start of the record groove, without damaging the recorded section of the groove.
Between each track on the recorded section of an LP record, there is usually a short gap of around 1 mm (0.04") where the groove is widely spaced. This space is clearly visible, making it easy to find a particular track.
Towards the label centre, at the end of the groove, there is another wide-pitched section known as the lead-out . At the very end of this section, the groove joins itself to form a complete circle, called the lock groove; when the stylus reaches this point, it circles repeatedly until lifted from the record. Automatic turntables rely on the position or angular velocity of the arm, as it reaches these more widely spaced grooves, to trigger a mechanism that raises the arm and moves it out of the way of the record.
The catalog number and stamper ID is written or stamped in the space between the groove in the lead-out on the master disc, resulting in visible recessed writing on the final version of a record. Sometimes the cutting engineer might add handwritten comments or their signature, if they are particularly pleased with the quality of the cut.
When auto-changing turntables were commonplace, records were typically pressed with a raised (or ridged) outer edge and label area. This would allow records to be stacked onto each other, gripping each other without the delicate grooves coming into contact, thus reducing the risk of damage. Auto changing turntables included a mechanism to support a stack of several records above the turntable itself, dropping them one at a time onto the active turntable to be played in order. Many longer sound recordings, such as complete operas, were interleaved across several 10-inch or 12-inch discs for use with auto-changing mechanisms, so that the first disk of a three-disk recording would carry sides 1 and 6 of the program, while the second disk would carry sides 2 and 5, and the third, sides 3 and 4, allowing sides 1, 2, and 3 to be played automatically, then the whole stack reversed to play sides 4, 5, and 6.
About the same time the most common substance for making 33 rpm disc records became vinyl, while 45 rpm discs were made from either vinyl or polystyrene. All speeds of records were made in various sizes, mainly 17.5, 25, 30 cm (~7, 10 and 12 inches diameter); the 17.5 cm (~7-inch) being most common for the 45 rpm, the 25 cm (~10-inch) for the 78 (and the first few years of 33â…“ production), and the 30 cm (~12-inch) for the 33 from the mid 1950s on.
The sound quality and durability of vinyl records is highly dependent on the quality of the vinyl. During the early 1970s, as a cost-cutting move towards use of lightweight, flexible vinyl pressings, much of the industry adopted a technique of reducing the thickness and quality of vinyl used in mass-market manufacturing, marketed by RCA Victor as the "Dynaflex" (125 g /mÂ²) process. Most vinyl records are pressed on recycled vinyl.
New "virgin" or "heavy" (180-220 g/mÂ²) vinyl is commonly used for classical music, although it has been used for some other genres. Today, it is increasingly common in vinyl pressings that can be found in most record shops. Many classic rock albums have been reissued on 180 g/mÂ² vinyl. Modern albums are also commonly pressed on 180 g/mÂ². Many collectors prefer to have 180 gram vinyl albums, and they have been reported to have a better sound than normal vinyl. These albums tend to withstand the deformation caused by normal play better than regular vinyl.
Since most vinyl records are from recycled plastic, it can lead to impurities in the record, causing a brand new album to have audio artifacts like clicks and pops. Virgin vinyl means that the album is not from recycled plastic, and will be devoid of the possible impurities of recycled plastic.
While most vinyl records are pressed from metal master discs, a technique known as lathe-cutting was introduced in the late 1980s by Peter King in Geraldine, New Zealand.  A lathe is used to cut microgrooves into a clear polycarbonate disc. Lathe cut records can be made inexpensively in small runs. However, the sound quality is significantly worse than proper vinyl records, and lathe cut records tend to degrade further in quality after repeated playing.
In 1958 the first stereo two-channel records were issued â€“ by Audio Fidelity in the USA and Pye in Britain, using the Westrex "45/45" single-groove system. While the stylus moves horizontally when reproducing a monophonic disk recording, on stereo records the stylus moves vertically as well as horizontally.
One could envision a system in which the left channel was recorded laterally, as on a monophonic recording, with the right channel information recorded with a "hill-and-dale" vertical motion; such systems were proposed but not adopted, due to their incompatibility with existing phono pickup designs (see below). In the Westrex system, each channel drives the cutting head at a 45 degree angle to the vertical. During playback the combined signal is sensed by a left channel coil mounted diagonally opposite the inner side of the groove, and a right channel coil mounted diagonally opposite the outer side of the groove. 
It is helpful to think of the combined stylus motion in terms of the vector sum and difference of the two stereo channels. Effectively, all horizontal stylus motion conveys the L+R sum signal, and vertical stylus motion carries the L-R difference signal. The advantages of the 45/45 system are:
This system was invented by Alan Blumlein of EMI in 1931 and patented the same year. EMI cut the first stereo test discs using the system in 1933. It was not exploited commercially until a quarter of a century later.
Stereo sound provides a more natural listening experience where the spatial location of the source of a sound is, at least in part, reproduced.
The development of quadraphonic records was announced in 1971. These recorded four separate sound signals. This was achieved on the two stereo channels by electronic matrixing , where the additional channels were combined into the main signal. When the records were played, phase-detection circuits in the amplifiers were able to decode the signals into four separate channels. There were two main systems of matrixed quadrophonic records produced, confusingly named SQ (by CBS) and QS (by Sansui). They proved commercially unsuccessful, but were an important precursor to later 'surround sound' systems, as seen in SACD and home cinema today. A different format, CD-4 (not to be confused with compact disc), by RCA, encoded rear channel information on an ultrasonic carrier, which required a special wideband cartridge to capture it on carefully-calibrated pickup arm/turntable combinations. Typically the high frequency information inscribed onto these LPs wore off after only a few playings, and CD-4 was even less successful than the two matrixed formats.
Under the direction of C. Robert Fine, Mercury Records initiated a minimalist single microphone monaural recording technique in 1951. The first record, Kubelik/Chicago's performance of "Pictures at an Exhibition" was described as "being in the living presence of the orchestra" by the NY Times music critic. The series of records was then named â€œMercury Living Presence.â€