Even if you haven’t heard of the Tristan chord, you’ve likely heard the sound itself. It was introduced to audiences on June 10, 1865, when Richard Wagner’s opera Tristan und Isolde premiered at the National Theatre in Munich, Germany, and its unconventional tonality went on to transform Western music.
The augmented sixth chord (F, B, D#, G#) is fairly simple in and of itself, but subverted the long-standing musical tradition of a dissonant chord quickly being resolved. In the case of Tristan und Isolde, a tragedy about two doomed lovers, that would have been too easy. Instead, the unresolved tension of the chord reflects the sense of longing and yearning seen throughout the plot. The tonally ambiguous chord opens the opera, and it isn’t resolved until the end of the nearly four-hour performance, when the sad story itself concludes.
To call this groundbreaking would be putting it lightly. The augmented sixth chord had been used by such luminaries as Mozart and Beethoven before, but had always quickly been resolved. Wagner, in keeping with his characters’ deep pain, chose to delay that resolution. This influenced later composers such as Claude Debussy, Arnold Schoenberg, and Alexander Scriabin, all of whom went on to influence generations of composers themselves, and the Tristan chord is still being analyzed today.
