earliest form of phonograph record, invented by Thomas A. Edison (Edison, Thomas Alva) in 1877. The sound to be recorded was focused by a horn onto a diaphragm, causing it to vibrate; the vibrations were transmitted to a stylus and modulated its motion as it followed a helical path along the surface of a yielding material (such as wax) that coated a cylinder rotating under the stylus. See also phonograph.