Questions: Diatonic Harmony and Roman Numeral Analysis

Question 1

In a major key, which scale degree produces a minor triad?

• A. I (tonic)
• B. IV (subdominant)
• C. V (dominant)
• D. ii (supertonic)

Answer: (D)

In a major key, chords built on scale degrees ii, iii, and vi are minor — they receive lowercase Roman numerals. I, IV, and V are major (uppercase). The ii chord, built on the second scale degree, is a minor triad, which is why it is written in lowercase. The tonic (I), subdominant (IV), and dominant (V) are all major.

Question 2

Roman numeral I typically refers to the note C.

• T. True
• F. False

Answer: False

Roman numerals describe harmonic function relative to the current key, not absolute pitches. I means the tonic chord of whatever key you are in — G major in G major, D major in D major, Bb major in Bb major. This transposability is exactly what makes Roman numeral analysis powerful: the same numeral pattern applies in every key.

Question 3

Why is the chord built on the seventh scale degree of a major key diminished rather than major or minor?

Model answer: It is built by stacking two minor thirds: from the leading tone up a minor third to the second scale degree, then another minor third to the fourth scale degree. Two stacked minor thirds produce a diminished triad.

In C major, vii° is B-D-F. B to D is a minor third (3 half steps); D to F is also a minor third (3 half steps). A major triad uses a major third then minor third; a minor triad uses a minor third then major third. The all-minor-thirds structure of vii° creates a diminished fifth (tritone) between B and F, giving the chord its strong instability and drive toward the tonic.