Most of our evidence for ancient Greek tragedy is from Athens, which in the classical period was the most important place of its performance. Athens was also where —towards the end of the sixth century BC— it came into being; or at least it was where there occurred the final phase of its genesis. Light on this genesis is provided by notices in ancient authors, the extant plays themselves, the shape of some early theatres, vase-paintings of choruses, and the evolution of drama in other cultures. The best evidence by far is the fourth chapter of Aristotle’s Poetics.
Aristotle states that tragedy had an improvisatory origin, and came into being from the exarchontes of the dithyramb. Aeschylus increased the n…
Seaford, Richard. "Origins of Greek Tragedy". The Literary Encyclopedia. First published 24 April 2009
[http://www.litencyc.com/php/stopics.php?rec=true&UID=5811, accessed 22 January 2017.]