The 12-inch (30 cm) single is a phonograph audio format played at 33⅓ or 45 rpm, with wider groove spacing than other records allowing greater dynamic range and volume.
The first 12-inch single is claimed to be ‘Straight from my heart’ by Swamp Dogg in 1973. This was a promotional copy of the 7-inch single, intended for DJs, and the B side was blank.
The first commercial 12-inch single release was in 1976 and was ‘Ten Percent’ by Double Exposure.
The 12-inch single was popular for disco music, and as well as the better dynamic range, the wider groove spacing assisted DJs in locating the approximate area of the ‘breaks’ on the disc’s surface.
Many record companies began producing 12-inch singles at 33⅓ rpm, as the slower speed enhances the bass on the record. However, 45 rpm gives better treble response and was used on many 12-inch singles, especially in the UK.
Increasingly in the 1980s, many pop and even rock artists released 12-inch singles that included longer, extended, or remixed versions of the actual track being promoted by the single. New Order’s Blue Monday, released in 1983, became the biggest-selling 12-inch single ever.