The process of recording signals on a medium through the use of light, so that the signals may be reproduced at a subsequent time. Photographic film has been widely used as the medium, but in the late 1970s development of another medium, the optical disk, was undertaken. The introduction of the laser as a light source greatly improves the quality of reproduced signals. Digital storage techniques make it possible to obtain extremely high-fidelity reproduction of sound signals in optical disk recording systems. This article first describes optical film recording and then some of the more modern optical recording methods.