Which chord is described as a diminished triad plus a diminished seventh?

• A. Diminished Seventh Chord
• B. Half Diminished Seventh Chord
• C. Diminished Triad Plus Diminished Seventh
• D. Dominant Seventh Chord

Answer: (A)

A fully diminished seventh chord is formed by adding a diminished seventh above the root to a diminished triad. This creates a four-note chord where each successive interval is a minor third, giving a symmetrical, tense sound. The description “diminished triad plus a diminished seventh” matches exactly this four-note sonority, and the conventional name for it is a diminished seventh chord (often called fully diminished seventh to emphasize its complete four-note structure). This distinguishes it from a half-diminished seventh, which uses a minor seventh instead of a diminished seventh, and from a dominant seventh, which uses a major triad with a minor seventh.