In terms of smaller roles, Bit players have small speaking roles, while Stand-ins take the place of actors for purposes of lighting and shot setup.
The acting role of the bit player is small (usually only one scene), with few lines or acting. This is in contrast to the role of cameo, extra, or walk-on.
The stand-in fills in for the main cast of the set, while the crew improves lighting, camerawork, and blocking. This valuable role enables efficient and effective filming and is an integral part of the film-making process. Stand-ins look at the actors during the rehearsal to see what they are doing and recreate it while the they are busy.
Film music can convey many emotions and settings, sadness and happiness, a rural countryside or a dark forest. Anything. Hope this helps in some way :)
