Record stylus playing record. Coloured scanning electron micrograph (SEM) of the needle (stylus) of a record player in a groove on a record. The grooves in the plastic vary in shape, and this is detected by the stylus and transformed to produce a variation in a sound output. The original groove was produced by reversing the process to record a sound input. In this way, a piece of music or song can be recorded as variations in a groove marked on a plastic disc. This record can then be played to reproduce the original sound. Magnification unknown.