Complex sentence: The band take off their masks and Schneider is relieved to see it is them, they start drinking, but the mood takes a turn as an unseen character (represented by the camera) enters mix to be beaten down by the band.
Split into simpler sentences: The band take off their masks and Schneider is relieved to see it is them. They start drinking, but the mood takes a turn as an unseen character (represented initially by the camera) enters the mix to be beaten down by the band.