Opera is a musical-theatrical form dependent upon language, but access to that language is mediated by texts and technologies. The singing body alone cannot disclose the sung text. The earliest surviving libretti demonstrate that reading played an important role in the audience's engagement with the new form, and over the ensuing four centuries reading has been opera's complicated but open secret. From seventeenth-century printed libretti to electronically delivered titles, reading has been a central component of performance practice and reception. This essay examines the history of reading at the opera - in the audience and within the diegesis - not as a prop for but as a function of operatic expression.