Roman Numeral Analysis
Roman numerals describe chords in relation to a key. C-G-Am-F in C major and E-B-C-sharp minor-A in E major both become I-V-vi-IV, so the harmonic pattern remains visible after transposition.
- 7 scale degrees
- quality shown by case
- pattern survives transposition
Where you run into this
- Every style
- Analysis
- Songwriting
- Session playing
The progression
- I
- V
- vi
- IV
Analyze in five steps
1. Establish the most convincing tonic from melody, bass, cadences and phrase endings.
2. Write the scale degrees of each chord root.
3. Identify chord quality: major, minor, diminished or augmented.
4. Add sevenths, extensions or inversion symbols when they matter.
5. Explain any chromatic chord through borrowing, tonicisation or another clear relationship.
Do not choose the key from the first chord alone. Loops can begin away from the tonic, and relative major and minor share many chords.
Case and symbols
In a common Roman-numeral system:
- uppercase I, IV and V indicate major triads
- lowercase ii, iii and vi indicate minor triads
- a small circle marks diminished, as in vii diminished
- 7 indicates a seventh chord
- accidentals alter the scale degree or root, as in bVII
In C major, the diatonic triads are I C, ii Dm, iii Em, IV F, V G, vi Am and vii diminished B diminished.
A worked example
Analyze C-G-Am-F in C major:
| Chord | Root degree | Quality | Numeral |
|---|---|---|---|
| C | 1 | major | I |
| G | 5 | major | V |
| Am | 6 | minor | vi |
| F | 4 | major | IV |
Transpose the numerals to G major and you get G-D-Em-C. No interval guessing is needed once the scale degrees are known.
Minor-key notation has two conventions
Classical analysis often treats the minor scale as the local diatonic reference. In A minor, C, F and G may be labelled III, VI and VII.
Popular-music analysis often measures roots against the parallel major scale. The same chords become bIII, bVI and bVII because A major contains C-sharp, F-sharp and G-sharp.
Both systems can be internally consistent. State the convention and do not switch midway through an analysis. Akousia commonly uses the parallel-major reference on progression pages because it makes modal alterations visible.
Inversions and slashes
Classical figured-bass symbols describe inversion: I6 is a tonic triad with its third in the bass, and I64 has its fifth in the bass.
Pop chord symbols use a slash note: C/E means a C major chord with E in the bass.
Roman-numeral slash notation can mean tonicisation: V/vi means the dominant of vi. In C major, V/vi is E major or E7 leading toward Am. Read the symbol system before interpreting the slash.
Chromatic chords
A chord outside the key is evidence, not an error.
bVII in C major: B-flat. It may suggest Mixolydian colour or borrowing from C minor.
V/vi in C major: E or E7. G-sharp acts as the leading tone of A and tonicises vi.
iv in C major: Fm. A-flat comes from the parallel minor and can lead chromatically to G in the tonic chord.
The numeral should support an explanation of sound and motion.