Richard Wagner (1813–83) was opera's most revolutionary figure. Dissatisfied with existing conditions and standards, he articulated his aspirations for the genre in numerous essays and introduced several reforms, eventually establishing the Bayreuth Festival (1876) specifically for the optimum performance of his works. Tristan und Isolde (1856–65) represents the quintessence of his mature style, summing up his innovations in both theory and practice and achieving a true synthesis of words and music. This exploration of the agony and ecstasy of erotic love, with its pervasive tonal ambiguity and restless chromaticism heightened by suspensions, unresolved dissonances and sequential variation, changed the course of music history, exercising a potent influence on succeeding generations of composers; more than any other work it symbolised the end of one era and the start of another.

Genesis: theory into practice

After the completion of Lohengrin (1848) Wagner composed no more music until his sketches for Das Rheingold (1853). The years between, though troubled ones (he was exiled from the German states until the early 1860s), were not creatively fallow. He contemplated his planned operas: Siegfrieds Tod (eventually Der Ring), Tristan und Isolde, Die Meistersinger von Nürnberg and Parsifal, as well as others eventually abandoned, and he wrote essays to explain why and how dramatic music should be developed from traditional ‘grand opera’ to what he termed ‘music drama’. These essays proved to be convenient progress benchmarks for him, even though, in the creative event, he sometimes bypassed them.