Visible crew/equipment: When the camera is focused on an actors face, most of the time you can see white screens and stage lights in their eyes.
Visible crew/equipment: Toward the end of the film, the 300 are in a shell style formation - Leonidas is in front, right before he removes his helmet, drops his spear and shield. It is obvious that the sun is shining on Leonidas and the 300 from behind, toward the ocean. But if you look into Leonidas' eyes you'll see white reflections - these are from reflector screens.
Answer: The scene is meant to show that Xerxes has exotic creatures/slaves from every corner of the world. In the reality of the film, a goat-headed musician would certainly qualify.