Widely acknowledged as one of the peaks of the operatic repertory, Tristan was notable for Wagner's advanced use of chromaticism, tonality, orchestral colour and harmonic suspension. Many see Tristan as the beginning of the move away from conventional harmony and tonality and consider that it lays the groundwork for the direction of classical music in the 20th century.
Act ISet on the deck of Tristan’s ship, on the voyage from Ireland to Cornwall, Isolde is traveling to Cornwall, where she is to be married, unwillingly, to Tristan’s uncle, King Marke. Beholding Tristan's apparent indifference, she resolves to kill him and herself, using one of her mother’s secret potions, which she bids her companion Brangäne to fetch. Brangäne, however, deceives her by producing a love potion instead. Summoning Tristan, Isolde pretends to accept her fate and proposes that they drink to in a pact of friendship. Expecting death, they gaze, love-struck, into each other’s eyes, and ecstatically embrace. As sailors’ shouts announce their journey’s end, Brangäne confesses her subterfuge and Isolde faints in Tristan’s arms. Act II
At King Marke’s castle in Cornwall the king and his retinue have set off on a hunting party. Deluded by passion into believing that darkness confers safety, honesty and true perception, the lovers lay their past to rest. When Brangäne confesses her unease, distraught that her switching of the potions has unleashed potential tragedy, Isolde assures her that her hand was guided by the power of true love, which rules all destiny. The lovers welcome the prospect of death, which will give them the total union and safe removal they crave. Their nocturnal dream is shattered by the return of Marke and his party, tipped off by a jealous ‘friend’, Melot, who denounces the lovers. After a surprisingly philosophical speech by the king, Tristan is allowed to return to Brittany, the land of his birth. But not before the enraged Melot seriously wounds him. Act IIITristan lies outside his castle by the sea, apparently lifeless. When a shepherd pipes a sad refrain, Tristan stirs. Kurwenal, his faithful squire, informs him that he has despatched a ship to fetch Isolde from Cornwall, for she alone, with her magic arts, can save him. When at last it arrives, Tristan, in agony, rises to greet her, fatally tearing the bandage from his wound. Reunited in each other’s arms, they share one final, love-locked gaze before Tristan sinks back lifeless on his couch. Tumultuous noises announce the arrival of a second ship, bearing Marke and his men, evidently in hot pursuit. In the ensuing mêlée, the ever-faithful Kurwenal is killed, never learning that Brangäne has informed the king of the love-potion and that he has arrived bearing forgiveness to them both.
Isolde is now beyond hearing, beyond caring. She sings with mounting rapture of joining her lover in death, before sinking, herself, lifeless on his corpse.