12 Inch

The 12-inch single gramophone record came into existence with the advent of disco music in the 1970s. The first 12" single was actually a 10" acetate used by a mix engineer (Jose Rodriquez) in need of a Friday night test copy for famed disco mixer Tom Moulton. more...

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As no 7" acetates could be found, a 10" blank was used. Mr. Moulton, feeling silly with a large disc that only had a few centimeters of groove on it, asked Rodriguez to re-cut it so the grooves looked more spread out. Because of the wider spacing of the grooves, a broader overall dynamic range (distinction between loud and soft) was made possible. This was immediately noticed to give a more favorable sound for discotheque play.

Mr. Moulton's position as the premiere mixer and "fix it man" for pop singles ensured that this fortunate accident would instantly become industry practice. This would perhaps have been a natural evolution: As the songs became much longer than the average pop song but the DJ in the club wanted a sufficient sound level (more precisely, greater dynamic range), the format would surely have had to be changed from the 175 mm (7 inch) single eventually.

It's also worth noting that the visual spacing of the grooves on the 12" assisted the DJ in locating the approximate area of the "breaks" on the discs surface (without having to listen as he dropped and re-dropped the stylus to find the right point). A quick study of any DJ's favorite discs will reveal mild wear in the "break points" on the discs surface that can clearly be seen by the naked eye and further eases the "cueing" (a club DJ's tone-arm cartridge will be heavily weighted and mild wear will seldom spoil the sound quality). Many DJ-only remix services such as Ultimix and Hot Tracks issued sets with deliberately visualised groove separations (the record was cut with narrow and wider spacings that could be seen on the surface, marking the mix points on the often multi-song discs).

A broader dynamic range or louder recording level requires more space as the grooves' excursions (i.e., the width of the groove waves and distance traveled from side to side by the turntable stylus) become much greater in amplitude --especially in the bass frequencies so important for dance music. Many record companies began producing 12-inch singles at 33 1/3 rpm, as the slower speed enhances the bass on the record. By the same token, however, 45 rpm gives better treble response and was used on many 12-inch singles, especially in the UK.

The first official promotional 12" single was Southshore Commissions "Free Man". At first, these special versions were only available as promotional copies to DJs. By 1976, with the release of "Ten Percent" by Double Exposure, the new format was sold to the general public. But also "Theme From Shaft" by Isaac Hayes (Stax 5C 052Z-62266 released 1971) could be one of the first.

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. These versions were frequently labelled with the parenthetical designation "12-inch version", "12-inch mix", "extended remix", "dance mix" or "club mix".

Read more at Wikipedia.org