was considered beautiful, even though he wrote exclusively in the Doric dialect, which was normally considered unpleasant to hear. The later poet Pindar of Thebes was renowned for his choral lyric poetry. Drama All surviving works of Greek drama were composed by playwrights from Athens and are written exclusively in the Attic dialect. Choral performances were a common tradition in all Greek city-states. The Athenians credited a man named Thespis with having invented drama by introducing the first actor, whose primary purpose was to interact with the leader of the chorus. Later playwrights expanded the number of actors to three, allowing for greater freedom in storytelling. In the age that followed the Greco-Persian Wars, the awakened national spirit of Athens was expressed in hundreds of tragedies based on heroic and legendary themes of the past. The tragic plays grew out of simple choral songs and dialogues performed at festivals of the god Dionysus. In the classical period, performances included three tragedies and one pastoral drama, depicting four different episodes of the same myth. Wealthy citizens were chosen to bear the expense of costuming and training the chorus as a public and religious duty. Attendance at the festival performances was regarded as an act of worship. Performances were held in the great open-air theater of Dionysus in Athens. The poets competed for the prizes offered for the best plays. All fully surviving Greek tragedies are conventionally attributed to Aeschylus, Sophocles or Euripides. The authorship of Prometheus Bound, which is traditionally attributed to Aeschylus, and Rhesus, which is traditionally attributed to Euripides, are, however, questioned. There are seven surviving tragedies attributed to Aeschylus. Three of these plays, Agamemnon, The Libation-Bearers, and The Eumenides, form a trilogy known as the Oresteia. One of these plays, Prometheus Bound, however, may actually be the work of Aeschylus's son Euphorion. Seven works of Sophocles have survived, the most acclaimed of which are the three Theban plays, which center around the story of Oedipus and his offspring. The Theban Trilogy consists of Oedipus the King, Oedipus at Colonus, and Antigone. Although the plays are often called a "trilogy," they were actually written many years apart. Antigone, the last of the three plays sequentially, was actually first to be written, having been composed in 441 BC, towards the beginning of Sophocles's career. Oedipus the King, the most famous of the three, was written around 429 BC at the