Roman Numeral Analysis: Understand Chord Progressions
Published March 4, 2026
Decode any chord progression using Roman numeral analysis. Learn how Roman numerals label chords by function, how to analyze songs in any key, and how this system makes transposition effortless.
Key Takeaways
- Roman numeral analysis labels chords by their scale degree position within a key.
- Uppercase = major, lowercase = minor, ° = diminished. The pattern is always the same in major keys.
- I-vi-IV-V is the most common pop progression, appearing in hundreds of hit songs.
- Roman numerals make transposition effortless — just change the starting key.
- Non-diatonic chords are written with chromatic alterations (bVII, V/V, etc.).
What Is Roman Numeral Analysis?
Roman numeral analysis is a system for labeling chords by their position (degree) within a key rather than by their specific letter names. Instead of saying 'C, Am, F, G', you say 'I, vi, IV, V'.
This system works for any key. The progression I-vi-IV-V sounds the same regardless of whether you play it in C (C-Am-F-G), G (G-Em-C-D), or any other key. The Roman numerals capture the functional relationship.
Uppercase Roman numerals indicate major chords. Lowercase indicates minor chords. A degree symbol (°) after the numeral indicates a diminished chord.
Roman Numerals in Major Keys
Every major key has the same diatonic Roman numeral pattern:
I (major) — Tonic. Home chord. The most stable and resolved.
ii (minor) — Supertonic. Subdominant function. Common in ii-V-I jazz progressions.
iii (minor) — Mediant. Tonic substitute. Less common but adds depth.
IV (major) — Subdominant. Movement away from home. Essential in pop and rock.
V (major) — Dominant. Maximum tension. Resolves strongly to I.
vi (minor) — Submediant. Relative minor. Tonic substitute. The 'sad' chord.
vii° (diminished) — Leading tone. Dominant function. Unstable and rarely used alone.
Example in C major: I=C, ii=Dm, iii=Em, IV=F, V=G, vi=Am, vii°=Bdim.
How to Analyze a Song
Step 1: Determine the key. Listen for the tonic chord (the one that sounds like home). This gives you your I chord.
Step 2: List every chord in the song by its letter name. Write them in order of appearance.
Step 3: Assign Roman numerals by counting up from the tonic. If the key is G major and you hear an Em, that is vi (the 6th degree).
Step 4: Identify the overall pattern. Most pop songs use 3-4 distinct chords. Common patterns: I-V-vi-IV, vi-IV-I-V, I-IV-V-I, I-vi-IV-V.
Step 5: Note any non-diatonic chords. A chord not found in the key will have a chromatic alteration (like V/V or bVII). These add color and interest.
Why Roman Numerals Are Essential
Transposition: Changing the key of a song becomes trivial. I-V-vi-IV in C (C-G-Am-F) is the same progression in A (A-E-F#-D). Just change the starting note.
Communication: Musicians worldwide speak the same language. 'Let us play a ii-V-I in Bb' is universal.
Pattern recognition: You start seeing the same progressions across thousands of songs. The I-vi-IV-V pattern appears in hundreds of pop hits.
Songwriting: Once you understand function, you can substitute chords freely. Replace I with vi, IV with ii — the progression still works because the functions are preserved.
Practice Exercises
- 1Analyze the chord progression of 'Let It Be' by The Beatles. Write each chord as a Roman numeral in the key of C major.
- 2Take the progression I-vi-IV-V and play it in four different keys: C, G, D, and A. Notice how the Roman numerals stay the same while the chords change.
- 3Pick a song and identify any non-diatonic chords. Try to explain why the songwriter included them (chromatic bass movement, secondary dominant, borrowed chord, etc.).
Common Mistakes
- Using uppercase for minor chords. Always check the chord quality: major gets uppercase (IV), minor gets lowercase (vi). The case communicates essential information.
- Assuming the first chord is always I. The first chord of a song is often IV or V. Find the tonic by listening for the chord that feels like home.
- Ignoring chord quality in analysis. Writing 'II' instead of 'ii' for a minor chord changes the entire analysis. Always verify the chord quality against the scale.
Frequently Asked Questions
Why are some Roman numerals uppercase and some lowercase?
Uppercase indicates a major chord, lowercase indicates a minor chord, and a degree symbol indicates a diminished chord. This reflects the chord quality that naturally occurs on each scale degree of the major scale.
What does a slash mean in Roman numeral analysis?
A slash indicates a chord inversion. V6/4 means the V chord in second inversion (5th in the bass). V6 means first inversion (3rd in the bass). The numbers refer to the interval between the bass note and the upper notes.
What are non-diatonic chords in Roman numeral analysis?
Non-diatonic chords are chords that contain notes outside the key. They are written with alterations: bVII (lowered 7th), V/V (secondary dominant of V), #IV (raised 4th). These add color but require understanding chromatic harmony.
Can I use Roman numeral analysis for minor keys?
Yes, but the pattern changes. Natural minor: i-ii°-III-iv-v-VI-VII. Harmonic minor: i-ii°-III+-iv-V-vi°-VII°. The lowercase pattern reflects the different chord qualities in minor keys.
How do I analyze a song with a key change?
Analyze each section in its own key. Mark the point of modulation and restart the Roman numeral analysis in the new key. For example: verse in C (I-IV-V-I) modulates to chorus in D (I-IV-V-I in the new key).