After the revolutionary events that took place in Dresden in the spring of 1849, Wagner was forced into exile in Zurich. In this Swiss city, between the months of October of 1850 and January of 1851, carried out the writing of which is considered like the key work of its theoretical-musical thought: Opera and drama. Throughout the three parts in which it is articulated, the brilliant German performs a weighty exposition of the ideas which, in his opinion, should support any operatic creation that really was considered such: the intimate union of text and melody; The problem of arias as elements of distortion of the unity of musical discourse; The importance of musical motifs in giving coherence and full meaning to the work ... Witness the importance that Wagner granted to this text, in which he spared no attacks on contemporary production, especially embodied in the figure of Meyerbeer, Are the words with which, after concluding, he presented it to Theodor Uhlig: "Here is my testament, now I can die." A fundamental work to understand the significance and transcendence of Richard Wagner's musical drama in the history of universal culture, this edition recovers the exceptional annotated translation that was made in 1995 by the Wagnerian ex angel, Ángel Mayo, an indisputable milestone. Unsurpassed of the studies on the German composer in Castilian language.