In music, a single is a type of release, typically a song 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, a single is a song that is released separately from an album, although it usually also appears on an album.
Typically, these are the songs from albums that are released separately for promotional uses such as digital download or commercial radio airplay and are expected to be the most popular. In other cases a recording released as a single may not appear on an album.
Despite being referred to as a single, in the era of digital distribution, singles can include up to as many as three tracks. The biggest digital music distributor, iTunes Store, accepts as many as three tracks less than ten minutes each as a single. Any more than three tracks on a musical release or thirty minutes in total running time is an extended play (EP) or, if over six tracks long, an album.
Historically, when mainstream music was purchased via vinyl records, singles would be released double-sided. That is to say, they were released with an A-side and B-side, on which two singles would be released, one on each side. Moreover, traditionally, only the most popular songs from a previously released album would be released as a single. In more contemporary forms of music consumption, artists release most, if not all, of the tracks on an album as singles.
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, and the standard diameter, 7 inches.
The 7-inch 45 rpm record was released 31 March 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 33 1⁄3 rpm 12-inch vinyl LP in June 1948, also released 33 1⁄3 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 7 December 1948 at the Sherman Avenue plant in Indianapolis, R.O. Price, plant manager. The claim made that 48-0001 by Eddy Arnold was the first 45 is evidently incorrect (even though as of this writing 48-0000 has not turned up) since all 45s were released simultaneously with the 45 player on the 29 March date. There was plenty of information 'leaked' to the public about the new 45 rpm system through front-page articles in Billboard magazine on 4 December 1948 and again on 8 January 1949. RCA was trying to blunt the lead Columbia had established in releasing their 33 1⁄3 LP system back in June 1948.
12-inch format
Although 7 inches remained the standard size for vinyl singles, 12-inch singles were introduced for use by DJs in discos in the 1970s. The longer playing time of these singles allowed the inclusion of extended dance mixes of tracks. In addition, the larger surface area of the 12-inch discs allowed for wider grooves (larger amplitude) and greater separation between grooves, the latter of which results in less cross-talk. Consequently, they are less susceptible to wear and scratches. The 12-inch single is still considered a standard format for dance music, though its popularity has declined in recent years.
