In a sense, western drama started with the chorus. In ancient Greece, according to Aristotle's Poetics, choral performances, consisting of groups of fifty or more people singing and dancing, would perform dithyrambs, or hymns honoring the god Dionysus on circular threshing floors known as orchestras, or dancing places. Choruses were normally segregated by gender and age, with girls', boys', and men's choruses each taking part in contests at the festival of Dionysus.
While the chorus normally performed as a group, eventually the chorus leader, or coryphaeus, began to speak lines on his own, and his role was transformed into that of an actor. The playwright Aeschylus added a second actor to choral performances, creating Greek theater in its classic form.
Classical drama consisted of two or three actors and choruses of 12 or 50 people. The dramas would alternate between episodes, in which the actors spoke, sometimes to each other and sometimes to the chorus, and choral odes in which the chorus would sing and dance. The members of the chorus were normally assigned generic roles, and would dress as elders of a city, average citizens, or other groups as demanded by the plot of the play.
In modern drama, the chorus still is an essential part of musical theater, and some modern playwrights such as Brecht employ choruses.