Thus all of Wagner's works, from "Der fliegende Holländer" to the "Ring der Niebelungen," have been located in the world of myth, in obedience to a profound art-principle. The opera of "Tristan and Iseult," first performed in 1865, announced Wagner's absolute emancipation, both in the construction of music and poetry, from the time-honoured and time-corrupted canons, and, aside from the last great work, it may be received as the most perfect representation of his school. The third main feature in the Wagner music is the wonderful use of the orchestra as a factor in the solution of the art-problem. This is no longer a mere accompaniment to the singer, but translates the passion of the play into a grand symphony, running parallel and commingling with the vocal music. Wagner, as a great master of orchestration, has had few equals since Beethoven; and he uses his power with marked effect to heighten the dramatic intensity of the action, and at the same time to convey certain meanings which can only find vent in the vague and indistinct forms of pure music. The romantic conception of the mediæval love, the shudderings and raptures of Christian revelation, have certain phases that absolute music alone can express. The orchestra, then, becomes as much an integral part of the music-drama, in its actual current movement, as the chorus or the leading performers. Placed on the stage, yet out of sight, its strains might almost be fancied the sound of the sympathetic communion of good and evil spirits, with whose presence mystics formerly claimed man was constantly surrounded. Wagner's use of the orchestra may be illustrated from the opera of "Lohengrin."