Terminology. Disc is frequently spelled disk,
most often in the area of digital technology, but sometimes in reference to phonograph records as well. In the present work disc
is used for the formats of sound recording. The earliest term for a flat circular object employed to receive and retain sound signals was phonautogram, from the Phonautograph invented by Léon Scott de Martinville in 1857. Scott’s device—which preserved a visual image of the sound waves only, without audio playback capability—...