A chorus is a group of nondescript characters in a Greek or Roman drama that narrates and provides commentary on the plot and action in the story. On one hand, the chorus provides the audience with an omniscient, background description of the story. On the other hand, the chorus functions as an actor who comments on the narrative and instructs the audience on what they are hearing and watching. Some argue that the chorus can be considered the voice of the author, depending on the drama. Horace recommends that the function of the chorus should be to “sustain the part and manly character of an actor: nor let them sing anything between the acts which is not conducive to, and fitly coherent with, the main design” (Lines 189-219, Paragraph 2).

An epistle is a text that is sent to a person or people, typically in a didactic form. This letter-writing genre of literature can be in prose or verse. Ars Poetica is a verse epistle addressed to the sons of Piso, a patron of