Principal parts on a Greek Tragedy

A Greek tragedy normally contained the following parts
(a) The prologue, the part before the entrance of the chorus, in monologue or dialogue setting forth the subject of the drama and the situation from which it starts. In the earliest tragedies the play begins with the entrance of the chorus, who set forth the subject.

(b) The song accompanying the entrance of the chorus

(c) The episodes, scenes in which one or more actors took part, with the chorus. The episodes might contain lyrical passages, lamentations, incidental songs by the chorus, etc.

(d) Songs of the chorus in one place i.e., in the orchestra as opposed to the first song which accompanied the entrance of the chorus. These songs were originally reflections or expressions of emotion evoked by the preceding episode. But this connection was gradually severed, until Agathon finally substituted mere musical interludes bctween the episodes.

(e) After the last choral song came the final scene