Horace’s Ars Poetica, composed around 15 B.C.E., guides potential poets in developing their art, and thereby reveals several conventions of favorable Roman poetry. It’s important to note that “poetry” here includes Roman drama.
First, he states that the aim of poetry should be to simultaneously delight and instruct its audience: “He who joins the instructive with the agreeable, carries off every vote, by delighting and at the same time admonishing the reader.” Here, Horace reveals that Roman poetry was valued by how well it merged aesthetic qualities with useful or practical insights. In Latin, these aims are dolce, or delight, and utile, or utility.
Next, Horace advises that poetry shouldn’t be protracted, but instead, concise. He reasons, “All superfluous instructions flow from the too full memory.” Whatever can’t be remembered isn’t useful; a poem or dramatic work should then be easy to recollect, and not be too excessive in length.
Finally, Horace insists that poetry should be harmonious, or possess a certain musical quality. At several points he instructs the reader in the use of stressed and unstressed syllables, and claims that one can always look to Homer for perfect examples of harmonious verse.