Were there any "Special Effects" in ancient Greek theatre?
There were two distinct “effects” other than the actors and chorus. First, the actors wore masks, which not only removed their own faces from the theatre language, but also allowed an actor to play more than one role—there are many occasions in the extant scripts that call for more than three roles, but the rule in the City Dionysia was that the producer/financier competing for the prize could not employ more than three actors (plus the chorus that stood for the citizens, etc.). There is some evidence that the masks included a primitive funnel-shape in the mouth to amplify the human voice, but that may be conjecture based on ignorance of the acoustic qualities of the theatres. Second, there was a Deus ex Machina (God from the Machine), a crane-hoist mechanical device for lowering an actor playing a god onto the stage.