Beginning in 1939, Columbia Records continued development of this technology. Dr. Peter Goldmark and his staff undertook exhaustive efforts to address problems of recording and playing back narrow grooves and developing an inexpensivereliable consumer playback system. In 1948, the 12" (30 cm) Long Play (LP) 33? rpm
microgroove record album was introduced by the Columbia Record at a dramatic New York press conference. In 1949, RCA Victor released the first 45 RPM single, 7" in diameter, with a large center hole to accommodate an automatic play mechanism on the changer, so a stack of singles would drop down one record at a time automatically after each play. Early 45 RPM music records were made from either vinyl or polystyrene.
The earliest rotation speeds varied widely. Most music records made in 1900–1925 were recorded at 74–82 revolutions per minute (RPM). However a few unusual systems were deployed. The Dutch Philips company introduced records whose rotational speed varied such that the reproducing "needle" ran at a constant linear velocity (CLV) in the groove. These records also, unusually, played from the inside to the outside. Both of these features were to be emulated by the modern day Compact Disc. The London Science Museum displays a Philips music record marked as "Speed D". It is one of these CLV disks.
In 1925, 78.26 rpm was chosen as the standard because of the introduction of the electrically powered synchronous turntable motor. This motor ran at 3600 rpm with a 46:1 gear ratio which produced 78.26 rpm. In parts of the world that used 50 Hz current, the standard was 77.92 RPM (3000 rpm with a 38.5:1 ratio), which was also the speed at which a strobe disc with 77 lines would "stand still" in 50 Hz light (92 lines for 60Hz). Thus these records became known as 78s (or "seventy-eights"). This term did not come into use until after World War II when a need developed to distinguish the 78 from other newer disc record formats, an example of a retronym. Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records. Standard records was also used, although the same term had also been used earlier for two-minute cylinders.