In music, a single or record single is a type of release, typically a recording of fewer tracks than an LP record or an album. This can be released for sale to the public in a variety of different formats. In most cases, the single is a song that is released separately from an album, but it usually appears on an album. Often, these are the most popular songs from albums that are released separately for promotional uses such as commercial radio airplay, and in other cases a recording released as a single does not appear on an album.
The basic parameters of the music single were made in the late 19th century, when the gramophone record began to supersede phonograph cylinders in commercial music. Gramophone discs were manufactured with a range of playback speeds (from 16 rpm to 78 rpm) and in several sizes (including 12-inch/30 cm). By around 1910, however, the 10-inch (25 cm) 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 3600 rpm with a 46:1 gear ratio, resulting in a rotation speed of 78.26 rpm.
With these factors applied to the 10-inch format, songwriters and performers increasingly tailored their output to fit the new medium. The 3-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 recordings. The breakthrough came with Bob Dylan's "Like a Rolling Stone", although CBS tried to make the record more "radio friendly" by cutting it in half and spreading it over both sides of the vinyl, both Dylan and fans demanded that the full six-minute take be placed on one side and that radio stations play the song in its entirety. "Like a Rolling Stone"'s subsequent success played a big part in changing the music business convention that singles had to be under three minutes in length.
Singles have been issued in various formats, including 7-inch (18 cm), 10-inch (25 cm) and 12-inch (30 cm) vinyl discs (usually playing at 45 rpm); 10-inch (25-cm) shellac discs (playing at 78 rpm); cassette, 8 and 12 cm (3- and 5-inch) CD singles and 7-inch (18 cm) plastic flexi discs. Other, less common, formats include singles on digital compact cassette, DVD, and LD, as well as many non-standard sizes of vinyl disc (5-inch/12 cm, 8-inch/20 cm, etc.).