What is the triad built on the seventh scale degree called?

What is the triad built on the seventh scale degree called?

• A. The major triad
• B. The minor triad
• C. The augmented triad
• D. The diminished triad

Answer: (D)

When you stack thirds on the seventh scale degree in a major-key context, the intervals above the root are a minor third and a diminished fifth. That combination defines a diminished triad. For example, in C major the seventh degree is B, and the triad B–D–F forms a diminished triad. This leading-tone triad is unstable and tends to resolve to the tonic, which is why it’s labeled as diminished. Note that in some natural-minor contexts the seventh degree can yield a different quality, but in the common practice framework this built-on-seventh triad is diminished.

When you stack thirds on the seventh scale degree in a major-key context, the intervals above the root are a minor third and a diminished fifth. That combination defines a diminished triad. For example, in C major the seventh degree is B, and the triad B–D–F forms a diminished triad. This leading-tone triad is unstable and tends to resolve to the tonic, which is why it’s labeled as diminished. Note that in some natural-minor contexts the seventh degree can yield a different quality, but in the common practice framework this built-on-seventh triad is diminished.