On the eight of June 1787 is successfully acted the première of Tarare, work due to the fertile collaboration between Beaumarchais and Salieri. Two months later is published a preface in which the librettist explains his ideas about opera in general, and his intentions concerning Tarare in particular. Does the text of this opera actually correspond to the declarations expressed by Beaumarchais in the preface ? Or, on the contrary, is the practice very different from the theory ? Our article aims at answering this question, after an investigation exploring four themes : the hierarchy of the different arts composing an opera ; the exoticism ; the blend of styles , lastly, the moral point of view.