During the seventeenth and eighteenth centuries, the models of Greek tragedy and Aristotelian theory were appealed to repeatedly, first to invent the dramatic genre we call opera, and then in an effort to use theory to rid that genre of what were perceived to be its self-indulgent excesses. This essay argues that despite these theoretical claims, influences from classical Rome were so thoroughly ingrained in European librettists that it was the experience of the Latin that prevailed. Roman subject matter, dramatic structure, philosophical fashion and imperial performance-context produced a musical theatre that was in essence Roman rather than Greek.