L.P. or Long Playing records are typically referred to as full length, 33 1/3 r.p.m. 12” albums. The LP format, originally introduced in 1948, by CBS Laboratories, in both 10” and 12” configurations, was designed to increase the quality of the existing 78r.p.m. 10” singles, by allowing for higher fidelity and customer convenience with an extended playing time.
The 33 1/3 r.p.m. 10” record began replacing the 78r.p.m. 10” single record as a format aimed at popular music buyers. The 12” 33 1/3 r.p.m. LP, was designed for higher priced classical recordings and Broadway Shows.
The average 33 1/3 r.p.m. 12”, has nearly 1,600 feet of groove per album, or about one third of a mile and shout be mastered with no more than 24 minutes of music per side, for maximum audio play back quality.