Modern theater as an art is often represented by two masks: a smiling comedy mask representing Thalia, the muse of comedy, and a frowning tragedy mask representing Melpomene, the muse of tragedy. These masks have their roots in the open air theater of ancient Athens, where they helped actors project broad emotions for large crowds while portraying multiple roles.
The worship of the god Dionysus in ancient Athens probably involved masks that represented the god to his followers. Dionysus was the Greek god of fertility that was closely associated with the harvest of grapes and the revelry fueled by wine. From the expressive (if not drunken) choruses sung at his festivals came the birth of drama and, eventually, theater performance. By the time of the playwright Aeschylus in the early 5th century B.C.E., various kinds of masks were used by actors in Athenian theater.
As worship developed into the Greek theater tradition, the masks took on new significance. Painted with exaggerated expressions, the masks helped actors broadcast their characters' emotions to viewers across the open air amphitheaters. The masks also allowed a small group of actors to portray a larger number of roles, independent of actual gender and age.
Although first meant to honor Dionysus, the theater masks have been associated with other deities over the past centuries. Janus, a two-faced god who represented doorways and gave us our name for the month January, lent his name to the pair, now often referred to as Janus masks. In modern theater tradition, the masks represent two of the nine muses (Mousai), Greek goddesses who inspired mankind in efforts such as music, poetry and dance.
The tragedy mask is typically referred to today as Melpomene, representing the muse of tragedy and, earlier, singing. Melpomene and her corresponding mask are often pictured along with cothurnuses, raised boots that gave the tragic actor a higher elevation on stage.
The comedy mask is typically referred to today as Thalia (Thaleia), the muse of comedy and idyllic poetry and sister of Melpomene. She and her mask are often represented with a thin shoe worn by comic actors to lower their stature on stage, or an ivy wreath, since ivy was emblematic of Dionysus and was usually given as an award during ancient Greek theater festivals.