Sentence:  The chorus, that is those members of the "komos" who have not become specialized as actors and continue singing and dancing, are headed by a <WSD>coryphaeus</WSD>, who sometimes addresses them, exhorting them to action, or to begin the song or the rite, or else anticipates or summarizes their words, or represents them in conversation with the actors. 
Meaning of the word marked with <WSD> tags:  The conductor or leader of the chorus of a drama.