Read a chord progression with Roman numerals

Roman-numeral chord labels describe harmony relative to a key. Here uppercase means a major triad, lowercase a minor triad, a small ° marks diminished and + marks augmented. The numeral follows the root's scale degree, even when another chord member is in the bass. Source: Open Music Theory, Roman Numerals.

Our first task supplies D major. Its scale is D–E–F♯–G–A–B–C♯. Number these notes 1–7 before labelling any chord. If you need to construct that collection, use the major-scale pattern guide. Do not infer the key merely because the first chord is D: the supplied key is part of this exercise's information.

Use two working columns: root degree and chord quality. A root on degree 6 does not by itself tell you whether its chord is major or minor. Read the complete chord name or inspect its notes, then combine the two answers.

The result is I–vi–IV–V. Check Bm especially: B is the sixth scale degree, while B–D is a minor third. Writing VI would keep B as the root but request a major triad, B–D♯–F♯. It would change D to D♯, not move the root to a different scale degree.

Keep “minor chord” and “minor key” separate. Bm is a minor chord within this supplied D-major setting. The lowercase vi does not change the exercise's key to B minor. Similarly, a major chord can appear within a minor-key setting.

Write F–G–A–B♭–C–D–E and number it 1–7. Read I–vi–IV–V one symbol at a time: choose root 1 and major quality, root 6 and minor quality, root 4 and major quality, then root 5 and major quality. This produces F–Dm–B♭–C.

A frequent copying error is to carry the old key's F♯ into Dm. Rebuild from the new key and specified quality instead. Another is to write B natural for IV: F major's fourth degree is B♭. To check triad spelling separately, revisit the four triad qualities.

For natural-minor examples here, the diatonic triads use i–ii°–III–iv–v–VI–VII. In tonal minor, raising the leading tone creates major V or diminished vii°; those labels conventionally reflect the raised leading tone. Source: minor-key Roman numerals. This is a stated convention, not permission to mix minor-numeral systems silently.

In supplied A minor, compare i–iv–v–i with i–iv–V–i. Their spellings are A–C–E, D–F–A, E–G–B, A–C–E for the first; change only G to G♯ in the third chord for the second. The root remains E. An uppercase V encodes that quality change without pretending A minor has become A major.

For chromatic prefixes in our major-key examples, ♭ or ♯ before a numeral lowers or raises its root relative to the supplied major scale; case still supplies chord quality. The sign need not become a literal flat or sharp in the root's final spelling. Source: analysing borrowed chords. Thus in D major, ♭VI is B♭ major, B♭–D–F. VI without the prefix would have B as root.

Some systems compare even minor-key roots with the parallel major scale and consequently use labels such as ♭III and ♭VI in minor. Our natural-minor labels above do not. Before borrowing an analysis from another chart, identify its reference scale. We do not analyse chromatically prefixed minor-key numerals in this exercise.

D3–F♯3–A3 and F♯2–A2–D3 both contain the D-major triad. Their root-degree and quality label in D major is I, but their bass notes differ. A fuller analysis can append inversion figures; our two-column exercise deliberately leaves inversion unmarked. Source: analysing root and optional inversion figures. See root, bass and inversions for that separate check.

The pattern I–vi–IV–V also leaves register, doubling, rhythm and phrase placement unspecified. It does not by itself prove which chord feels like a destination, that a particular cadence occurred, or that the supplied tonic would be the only plausible hearing of an unfamiliar song. Those questions need the surrounding music. First make the label accurate; then gather the context needed for a functional analysis.

1. In supplied G major, label G–Em–C–D. Spell every chord.
2. Recover ii–V–I in supplied B♭ major, including every accidental.
3. In D major, what changes between vi and VI?
4. Can the bare root-and-quality label IV tell you the chord's lowest note?

Check the conversion answers

1. I–vi–IV–V. G–B–D; E–G–B; C–E–G; D–F♯–A.
2. Cm–F–B♭: C–E♭–G; F–A–C; B♭–D–F. B♭ major contains both B♭ and E♭.
3. B–D–F♯ becomes B–D♯–F♯. The root remains degree 6; the quality becomes major.
4. No, not in this exercise's deliberately inversion-free notation. Inspect the actual voicing or an explicit inversion/bass instruction.

Use the two-key worksheet and answer key. Cover the answers, complete root degree and quality separately, then compare both columns before accepting a numeral.