Why are musical performances in movies often recorded before filming begins?

Musical performances in movies are typically recorded before filming begins because of the technical demands of the production process. Filming is rarely a continuous event; instead, a performance is broken down into numerous individual shots that can take hours to prepare. Attempting to record a live, continuous musical performance during these fragmented shooting sessions would be extremely difficult.1

By prerecording the songs and accompaniment, filmmakers create a playback track. During the actual filming, performers simply mouth the words or mimic playing their instruments in synchronization with this pre-existing audio. This method ensures that the music remains consistent and perfectly timed across various camera angles and takes, allowing the production team to focus on visual composition without the logistical challenges of capturing high-quality live audio on a busy film set.1