Good Morning
Sorry If I wasn’t clear on the question, There was a 4 camera shoot, audio was recorded through the camera. The board tracks were recorded in studio. Video and audio were captured in FCP. Camera sound was pulled and replaced with the board tracks which recorded in studio at an earlier date. The board tracks did not sync with the audio (sample rates were different). The editor increased the speed of the video to compensate. It may work for the vocals, but does it change the beat of the instrumentals and thus cause it to be out of sync.
SjDemar