Questions: Triads: Major, Minor, Diminished, Augmented

Question 1

Which of the following correctly describes the interval structure of a diminished triad built on C?

• A. C-E-G (major third + minor third)
• B. C-E♭-G (minor third + major third)
• C. C-E♭-G♭ (minor third + minor third)
• D. C-E-G♯ (major third + major third)

Answer: (C)

A diminished triad consists of two stacked minor thirds. From C: up a minor third is E♭, and up another minor third from E♭ is G♭. Option A is a major triad, option B is a minor triad, and option D is an augmented triad. The interval structure — not the note names — defines the triad quality.

Question 2

Any three pitches played simultaneously form a triad.

• T. True
• F. False

Answer: False

A triad requires a specific interval structure: two thirds stacked on top of each other (either major or minor in some combination). Three arbitrary pitches — say, C, D, and F♯ — do not form a triad because they are not organized as stacked thirds. A triad is a harmonic structure, not merely a count of notes.

Question 3

What is the structural difference between a major and a minor triad, and how does that difference affect the character of each?

Model answer: A major triad has a major third on the bottom and a minor third on top. A minor triad reverses this: minor third on the bottom, major third on top. Lowering the middle note (the third of the chord) by a half step converts a major triad to minor, shifting the character from bright and stable to darker and more somber.

The fifth is the same size in both major and minor triads (a perfect fifth from root to top), so the outer frame is identical. Only the middle note — the chord's third — changes. This is why minor sounds like a 'shadowed' version of major on the same root: the outer structure is shared, but the inner division is inverted.