What does Ode 1 of Sophocles's "Oedipus Rex" contribute to the play?I'm in need of a thesis, but I do not really understand the ode.

The chorus in this play, who chant the song or ode, represent the elders of the city of Thebes.  These choral odes and dances serve to separate one scene from another as there was no curtain in the Greek theatre.  They also comment on the action, reinforce the emotion, and interpret the situation.  Sometimes the chorus even participates in dialogue with other characters; when they do, their lines are spoken by the Coragos, or leader.

Thus, the first Ode of "Oedipus Rex" presents the dilemma of the people of Thebes who suffer from endless "afflictions."  There is a plague on the town, and the people pray that the "besieger" will be "plunged from our homes/Into the vast sea-room of the Atlantic/Or into the waves that foam eastward of Thrace/...Destroy our enemy,lord of the thunder![Apollo] (STROPHE 3)

As Oedipus the King enters, he asks the people, "Is this your prayer?"  Then, he tells the people to listen to him, for he will provide relief from their evils, he promises.  In the scope of the tragedy of "Oedipus Rex," the first Ode provides the problem of the play, while contributing to the irony of the prophecy against Oedipus.  In other words, all the conflicts are set in motion after the introduction of this Ode.  The hamartia, or arrogance of Oedipus is apparent as he summarily promises that he will solve this problem.  Later, his tragic downfall comes as a result of his pride and failure to realize that he is the cause of this very problem.  In short, the PARODOS (Ode 1) is pivotal to the plot and tragedy of Oedipus Rex.