The Chorus in the play Oedipus has a few important functions. The chorus is set in the play to act as bystanders throughout the play, observing what goes on, reacting and offering opinions at regular intervals throughout the play. In this role they are important to the play as they often offer the voice of reason during moments of heated debate, the voice of fear and confusion during Oedipus' downfall, which seems to mirror the audience's reaction and emotion in many situations throughout the play. The Chorus is also used as a sort of audience for passages of description over what has gone on but hasn't been introduced to the reader for instance after Jocasta has realized the truth the second messenger describes the scene inside the palace to the Chorus: "Within the porch, straight to the couch she rushed, her bridal bed, and tore her hair.".
The Chorus offers a sort of narrative for the audience. This function is equally important to the success of the play. The Chorus often speaks in this way at the end of a scene to clarify what has just gone on. For instance at the end of the first scene, the chorus clarifies the diseased state that the city of Thebes has encountered, "Still breeding plague, unpitied infants lie.and wives and mothers, gray with hoary age.by every alter mourn.".
The Chorus is used to keep the stability during the play. In modern theatre, the plays are normally split up into scenes and acts. However, the Greek kept the continuity between these gaps, by having a narrative section. This prevented the need of having breaks in the action and also kept the audience up to date with what had just gone on, and offering some insight or other. In this role, the Chorus is very helpful to the audience.
In the play Oedipus, Sophocles intended the Chorus to be a constant significant part of the play, observing and reacting to situations, at the same time as never being the center of attention during the main story, and only coming into the play during the narrative parts of the play.