In 1886 Berliner began experimenting with methods of
sound recording. He was granted his first
patent for what he called the "
Gramophone" in 1887. The patent described recording sound using horizontal
modulation of a
stylus as it traced a line on a rotating
cylindrical surface coated with an unresisting opaque material such as
lampblack, subsequently fixed with
varnish and used to
photoengrave a corresponding groove into the surface of a metal playback cylinder. In practice, Berliner opted for the disc format, which made the photoengraving step much less difficult and offered the prospect of making multiple copies of the result by some simpler process such as
electrotyping, molding or stamping. In 1888 Berliner was using a more direct recording method, in which the stylus traced a line through a very thin coating of wax on a zinc disc, which was then etched in acid to convert the line of bared metal into a playable groove. (
Source)