In many Greek tragedies, the Chorus serves an important role. It is used for many things, such as clarifying the feelings of the characters and to establish and point out the significance of facts in the story. In Oedipus the King, the Chorus serves these functions, as well as to give the reader insight into the beliefs of the ancient Greeks.
The functions of the Chorus are not just for dramatic purposes. The Chorus was first used in Greek tragedies for the sake of the audience. In ancient Greece, plays were performed in large amphitheaters that would seat around ten thousand people. The actors had no way of projecting their voices, so a group of actors would read the lines together. This made it easier for the whole audience to hear what was being said (Wat).
As playwrights developed the concepts of individual actors, the role of the Chorus was reduced.
However, they still had an important role in the play. The playwrights used the Chorus to establish facts in the play, to clarify certain events, to reflect the society's outlook, to give insight into a character's emotions, and to point out important events as they occur (Wat).
This is especially evident in Oedipus the King. On page nine, the Chorus has its first speaking part in the play (which is known as the parados), and it is invoking the Gods and asking them for help. A plague befell the city of Thebes in which their crops and people were dying. The Oracle of Delphi said that the plague would only end when the killer of Laius (the former king of Thebes) was found. Here, the Chorus is giving the reader insight into Greek culture: O Prophecy of Jove, whose words are sweet, With what doom art thou sent...