LP record
The LP (from "long playing"[1] or "long play") is an analog sound storage medium, specifically a phonograph record format characterized by: a speed of 33+1⁄3 rpm; a 12- or 10-inch (30- or 25-cm) diameter; use of the "microgroove" groove specification; and a vinyl (a copolymer of vinyl chloride acetate) composition disk. Introduced by Columbia Records in 1948, it was soon adopted as a new standard by the entire US record industry and, apart from a few relatively minor refinements and the important later addition of stereophonic sound in 1957,[2] it remained the standard format for record albums during a period in popular music known as the album era.[3] LP was originally a trademark of Columbia[4] and competed against the smaller 7-inch sized "45" or "single" format by RCA Victor, eventually ending up on top.[5] Today in the vinyl revival era, a large majority of records are based on the LP format and hence the LP name continues to be in use today to refer to new records.[6][7]
This article is about vinyl records. For music albums in general, see Album.Media type
Audio playback
Analog groove modulation
Originally 23 minutes per side, later increased by several minutes, much longer possible with very low signal level
Microgroove stylus (maximum tip radius 0.001 in or 25 μm)
12 in (30 cm), 10 in (25 cm), 90–240 g (3.2–8.5 oz)
Audio storage
1948
Format advantages[edit]
At the time the LP was introduced, nearly all phonograph records for home use were made of an abrasive (and therefore noisy) shellac compound, employed a much larger groove, and played at approximately 78 revolutions per minute (rpm), limiting the playing time of a 12-inch diameter record to less than five minutes per side. The new product was a 12- or 10-inch (30 or 25 cm) fine-grooved disc made of PVC ("vinyl") and played with a smaller-tipped "microgroove" stylus at a speed of 33+1⁄3 rpm. Each side of a 12-inch LP could play for about 22 minutes.[8]
Playing time[edit]
With the advent of sound film or "talkies", the need for greater storage space made 33+1⁄3 rpm records more appealing. Soundtracks – played on records synchronized to movie projectors in theatres – could not fit onto the mere five minutes per side that 78s offered. When initially introduced, 12-inch LPs played for a maximum of about 23 minutes per side, 10-inch records for around 15. They were not an immediate success, however, as they were released during the height of the Great Depression, and seemed frivolous to the many impoverished of the time. It was not until "microgroove" was developed by Columbia Records in 1948 that Long Players (LPs) reached their maximum playtime, which has continued to modern times.[36]
Economics and tastes initially determined which kind of music was available on each format. Recording company executives believed upscale classical music fans would be eager to hear a Beethoven symphony or a Mozart concerto without having to flip over multiple, four-minute-per-side 78s, and that pop music fans, who were used to listening to one song at a time, would find the shorter time of the 10-inch LP sufficient. As a result, the 12-inch format was reserved solely for higher-priced classical recordings and Broadway shows. Popular music continued to appear only on 10-inch records. However, by the mid-1950s, the 10-inch LP, like its similarly sized 78 rpm cousin, lost the format war and was discontinued.[37]
Groove[edit]
The close spacing of the spiral groove that allowed more playing time on a 33+1⁄3 rpm microgroove LP also allowed a faint pre-echo of upcoming loud sounds. The cutting stylus unavoidably transferred some of the subsequent groove's signal to the previous groove. It was discernible by some listeners throughout certain recordings, and a quiet passage followed by a loud sound would allow anyone to hear a faint pre-echo of the loud sound 1.8 seconds ahead of time.[38]
The following are some significant advances in the format: