The Tristan chord is based on which type of chord?

• A. Half-diminished seventh chord
• B. Dominant seventh chord
• C. Major triad with added sixth
• D. Minor triad

Answer: (A)

Think of a half-diminished seventh as a diminished triad with a minor seventh added. The Tristan chord fits this shape: for example, B–D–F–A stacks a diminished triad (B–D–F) with a minor seventh above the root (A above B). This four-note sonority has a tense, unresolved quality that Wagner uses to blur traditional dominant-to-tonic expectations, rather than functioning like a true dominant seventh or a simple major/minor triad. So the best description is a half-diminished seventh chord.