In a sense, avant-garde music is a rear-, not an advance-guard action, for it is both a consequence of, and a reaction against, five hundred years of European ‘consciousness’. The Renaissance started with man's dualistic awareness of the distinction between the Self and the Non-Self: which in musical terms became the dualistic, and peculiarly European, phenomenon of harmony. Perhaps this burden of harmonic consciousness begins to work itself out in Wagner's Tristan. At the opening of the third act, Tristan lies in a state of near paralysis in his cobwebby castle, and hears the unaccompanied monody of the Shepherd's pipe. Alternating shiftily between God's perfect fifths and fourths and the Devil's imperfect ones, it is a ‘horizontal’ sublimation of the dualism of the notorious ‘Tristan’ chords. Harmonic resolution, after four and a half hours, is at last achieved, and Tristan sheds sensuality and guilt to enter Nirvana. Debussy's Pelléas et Mélisande, an opera closely related to Tristan, carries the process a stage further, for although harmonically sensuous, it dispenses with even the desire for resolution. It's a premature existential opera, for it concerns, both dramatically and musically, what happens to passion when the will is extinct.