Lip sync
Lip sync, lip-sync, lip-synch (short for lip synchronization) is a technical term for matching lip movements with pre-recorded sung or spoken vocals that the listeners hear through speakers, either through PA system speakers in a "live" performance or television or cinema speakers in the case of a lip-synced TV show or film performance. The term can refer to any of a number of different techniques and processes, in the context of live performances and recordings.
In film production, lip synching is often part of the post-production 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-synced sound files to create an immersive environment. In the case of the music industry, lip-synching can be controversial to fans attending live concert performances who expect to view a live performance.
In music
Lip-synching, is often featured and considered a part of miming, and can be used to make it appear as though actors have substantial musical ability (e.g., The Partridge Family), to create particular vocal effect that can only be achieve in the recording studio, to improve performance during live dance numbers that also incorporate vocals, to misattribute vocals entirely (e.g. Milli Vanilli), or to cover for deficiencies during live performance. It is also commonly used in drag shows. 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, however, lip sync because they are not as confident singing live and may wish to avoid possible bad notes.