Poetics (6.2-6.6)

Tragedy is, then, a representation of an action[*] that is heroic and complete and of a certain magnitude—by means of language enriched with all kinds of ornament, each used separately in the different parts of the play: it represents men in action and does not use narrative, and through pity and fear it effects relief to these and similar emotions.[*]

By language enriched I mean that which has rhythm and tune, i.e., song,

and by the kinds separately I mean that some effects are produced by verse alone and some again by song.

Since the representation is performed by living persons, it follows at once that one essential part of a tragedy is the spectacular effect, and, besides that, song-making and diction. For these are the means of the representation.

By diction I mean here the metrical arrangement of the words; and song making I use in the full, obvious sense of the word.