In December 1856, when Wagner was at work on the first act of Siegfried, he became obsessed with a melodic idea he associated with the legend of Tristan and Isolde. He subsequently broke away from his work on the Ring Cycle until his opera based on Tristan and Isolde was completed.

The Prelude and Liebestod (or Love-Death) constitutes the very beginning and end of the opera, in an orchestral combination that was sanctioned by the composer as a separate entity for performance in its own right. The Prelude depicts the unvoiced longing of Tristan and Isolde for one another, and with the Liebestod, or 'Love-Death'comes the fulfilment of that longing in their death together, their immortal love being voiced by Isolde as she stands over Tristan's corpse, contemplates his transfigured soul, and joins it by taking her own life. The work is widely considered among the most powerful and emotionally gripping music ever written.