In music, a single is a type of release, typically a song recording of fewer tracks than an LP record or an album. One can be released for sale to the public in a variety of formats. In most cases, a single is a song that is released separately from an album, although it usually also appears on an album. In other cases a recording released as a single may not appear on an album.
With the rise of digital distribution, distinctions have become more tenuous. The biggest digital music distributor, the iTunes Store, only accepts releases with three tracks or fewer that are less than ten minutes each as a singles (with longer releases being classified as EPs or albums). However, releases which do not fit these criteria have been promoted as singles by artists and labels elsewhere, such as on the Bandcamp storefront.
Historically, when mainstream music was purchased via vinyl records, singles would be released double-sided, i.e. there was an A-side and a B-side, on which two songs would appear, one on each side.
Early history
The origins of the single are in the late 19th century, when music was distributed on phonograph cylinders that held two to four minutes' worth of audio. They were superseded by disc phonograph records, which initially also had a short duration of playing time per side. In the first two to three decades of the 20th century, almost all commercial music releases were, in effect, singles (the exceptions were usually for classical music pieces, where multiple physical storage media items were bundled together and sold as an album). Phonograph records were manufactured with a range of playback speeds (from 16 to 78 rpm) and in several sizes (including ). By about 1910, however, the , 78-rpm shellac disc had become the most commonly used format.
The inherent technical limitations of the gramophone disc defined the standard format for commercial recordings in the early 20th century. The relatively crude disc-cutting techniques of the time and the thickness of the needles used on record players limited the number of grooves per inch that could be inscribed on the disc surface and a high rotation speed was necessary to achieve acceptable recording and playback fidelity. 78 rpm was chosen as the standard because of the introduction of the electrically powered synchronous turntable motor in 1925, which ran at 3,600 rpm with a 46:1 gear ratio, resulting in a rotation speed of 78.3 rpm.
With these factors applied to the 10-inch format, songwriters and performers increasingly tailored their output to fit the new medium. The three-minute single remained the standard into the 1960s, when the availability of microgroove recording and improved mastering techniques enabled recording artists to increase the duration of their recorded songs. The breakthrough came with Bob Dylan's "Like a Rolling Stone": although Columbia Records tried to make the record more "radio-friendly" by cutting the performance into halves and separating them between the two sides of the disc, both Dylan and his fans demanded that the full six-minute take be placed on one side and that radio stations play the song in its entirety.
Types of physical singles
Singles have been issued in various formats, including , 10-inch and 12-inch discs, usually playing at 45 rpm; 10-inch shellac discs, playing at 78 rpm; maxi singles; 7-inch plastic flexi discs; cassettes; and CD singles. Other, less common, formats include singles on Digital Compact Cassette, DVD and Laserdisc, as well as many non-standard sizes of vinyl disc (, , etc.).
7-inch format
The most common form of the vinyl single is the "45" or "7-inch". The names are derived from its play speed, 45 rpm (revolutions per minute), and the standard diameter, .
The 7-inch 45 rpm record was released March 31, 1949, by RCA Victor as a smaller, more durable and higher-fidelity replacement for the 78 rpm shellac discs. The first 45 rpm records were monaural, with recordings on both sides of the disc. As stereo recordings became popular in the 1960s, almost all 45 rpm records were produced in stereo by the early 1970s. Columbia Records, which had released the rpm 12-inch vinyl LP in June 1948, also released rpm 7-inch vinyl singles in March 1949, but they were soon eclipsed by the RCA Victor 45. The first regular production 45 rpm record pressed was "PeeWee the Piccolo": RCA Victor 47-0146 pressed December 7, 1948 at the Sherman Avenue plant in Indianapolis; R.O. Price, plant manager.