Definitions for "12-inch single"
The 12-inch [30 cm] 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. As no 7" acetates could be found, a 10" blank was used.