The phonograph record was the primary medium used for music reproduction throughout the 20th century. It had co-existed with the phonograph cylinder from the late 1880s and had effectively superseded it by around … 詳細

Early speeds
Early disc recordings were produced in a variety of speeds ranging from 60 to 130 rpm, and a variety of … 詳細

Shellac
One problem with shellac was that the size of the disks tended to be larger because it was limited to 80–100 groove walls per inch before the risk of … 詳細

Manufacture of disc records began in the late 19th century, at first competing with earlier cylinder records. Price, ease of use and storage made the disc … 詳細

CBS Laboratories had long been at work for Columbia Records to develop a phonograph record that would hold at least 20 minutes per side. 詳細

Types of records
The usual diameters of the holes on an EP record are 0.286 inches (7.26 mm).
Sizes of records in the United States and the UK are generally measured in inches, e.g. 7-inch records, which are generally 45 rpm records. LPs were … 詳細

Increasingly from the early 20th century, and almost exclusively since the 1920s, both sides of the record have been used to carry the grooves. Occasional records have been issued since … 詳細