The actors and the chorus
At first in dithyramb, there were no actors. Thespis was the poet who introduced the first hypocrite, Aeschylus the second and Sophocles the third one. Besides these actors, who were playing the leading parts, there were also some other persons on the orchestra (=stage), playing "dumb" roles (the "followers").
At the beginning the actors have been chosen by the poets (they -sometimes- played the roles themselves). Later, when theatre competition became tough, the need of professional actors emerged. Some actors tended to attach themselves to a poet. Still in the 5th century, when the success of a production depended on the actors as well, they were being chosen by the State.
The hypocrites were always men, even if they were playing female roles. In order to have a female appearance, they were playing wearing the "prosternida" (before the chest, imitating a woman's breasts) and the "progastrida" before the belly. In order to look taller and more impressive they were wearing "cothornous" (wooden shoes with tall heels). These shoes were the same for both legs (no right and left). They were dressed in long robes with vertical stripes.
The most essential part of their disguise was the mask These masks were made ad hoc and they had big holes for the mouth and the eyes. The mask was absolutely necessary as it was necessary in the Dionysian religion.
Actors and especially the ones who played the leading parts ("protagonists") were persons of high respect, not only to the Athenian society but worldwide. Some of them have been addressed as ambassadors. In the 5th century they had become significant members of the greek society and they have been very rich, since they were very well payed.
Up to the point when Sophocles imported his innovations in drama, the chorus had 12 members. Sophocles added three more. The 15 members of the chorus were entering the orchestra in rows ( usually face=3, depth=5 ), which means that although in old dithyramb the chorus was making a circle, in ancient theater the chorus was making squares. The leader of the chorus ("Coryphaios") was in the middle of the first row. Coryphaios was a professional dancer and singer. The rest of the chorus consisted of amatures chosen by the poet and payed by the sponsor (choregos)
The chorus was entering from the two "parodoi". His appearance was depending on the play. For the tragedy the chorus was very solemn and it was called "emmelia". In comedies it was funny and it was called "codrax", when in satiric drama it was scoptic and it was called "sicinnis".
The chorus, was considered to be the mouthpiece of society (in its humble form) and morality, and they were suffering along with the heroes. Its role (very important at first) was fading during the time