Lip sync or lip synch is a technical term for matching a speaking or singing person's lip movements with sung or spoken vocals. Audio for lip syncing is generated through the sound reinforcement system in a live performance or via television, computer, cinema speakers, or other forms of audio output. The term can refer to any of a number of different techniques and processes, in the context of live performances and audiovisual recordings.
In film production, lip-synching is often part of the postproduction phase. Dubbing foreign-language films and making animated characters appear to speak both require elaborate lip-synching. Many video games make extensive use of lip-synched sound files to create an immersive environment in which on-screen characters appear to be speaking. In the music industry, lip-synching is used by singers for music videos, television and film appearances and some types of live performances.
Sometimes lip sync performances are forced on performers by television producers to shorten the guest appearances of celebrities, as it requires less time for rehearsals and hugely simplifies the process of sound mixing, or to eliminate the risk of vocal errors. Some artists lip sync because they are not confident singing live and want to avoid singing out of tune.
Because the film track and music track are recorded separately during the creation of a music video, artists usually lip-sync their songs and often imitate playing musical instruments as well. Artists also sometimes move their lips at a faster speed than the recorded track, to create videos with a slow-motion effect in the final clip, which is widely considered to be complex to achieve. Similarly, some artists have been known to lip-sync backwards for music videos such that, when reversed, the singer is seen to sing forwards while time appears to move backwards in his or her surroundings.