The ‘Tristan' Chord, is any chord that consists of the intervals:
‘Augmented fourth, ‘Augmented sixth, and ‘Augmented ninth, above a ‘Bass note.
It is so named, as it is heard in the opening phrase of ‘Richard Wagner's ( Vahg-Ner’s ) ‘Opera, "Tristan und 'Isolde", as part of the *leitmotif relating to ‘Tristan.
Unlike the ‘Quartal Voicing, of ‘Miles Davis’s, "So What" Chord, that is stacked in, ‘Perfect Fourths... and part of my investigation of ‘Non-Tertiary Chords', that are, ( Stacked in 3rd s )...
*Definition of leitmotif. 1 : an associated melodic phrase or figure that accompanies the reappearance of an idea, person, or situation especially in a Wagnerian music drama. 2 : a dominant recurring theme.