Sentence:  Post-classical references to the famous ‘chorus-trainer' Sannio indicate that his role extended to performing and thus taking the <WSD>coryphaeus</WSD> role. The <WSD>coryphaeus</WSD> was both leader and teacher, and in performance played a crucial role in setting the time that the other dancers followed. 
Meaning of the word marked with <WSD> tags:  The conductor or leader of the chorus of a drama.