Roman numeral analysis

The system

Roman numerals refer to scale degrees, not specific chords. I = first chord of the key, ii = second chord, etc.

• Uppercase = major triad: I, IV, V
• Lowercase = minor triad: ii, iii, vi
• ° (degree symbol) = diminished: vii°
• Add “7” for 7th chord: Imaj7, ii7, V7, vi7…
• Flat or sharp before numeral = altered root: ♭III, ♭VI, ♭VII, etc.
• Slash for inversion: V/IV (the V of IV), I/3 (first inversion)

A few examples:

• “I-IV-V” in C major = C - F - G
• “ii-V-I” in F major = Gm - C7 - F
• “i-♭VII-♭VI-V” in A minor = Am - G - F - E

The benefit

When you analyse a song, you don’t write down the chord letters — you write the functions. This way, the same Roman-numeral pattern can be played in any key.

A working musician sees “I-V-vi-IV” and knows what to play in any key — even one they’ve never played the song in. Try doing that with “C-G-Am-F” alone.

Common labelled progressions

Once you’re fluent in Roman numerals, songs become tags:

• The “Axis” / pop-punk: I-V-vi-IV
• The “doo-wop” / “50s”: I-vi-IV-V
• The “Andalusian cadence”: i-♭VII-♭VI-V (in minor) — flamenco, prog rock
• The “ragtime/blues turnaround”: I-VI-ii-V (cycle of fifths fragment)
• The “circle of fifths”: Imaj7-IV7-vii°-iiim7-vim7-iim7-V7-Imaj7 (full descending circle)

Inversions and secondary dominants

Two more notational layers you’ll see:

Inversion is shown by a slash or by figured-bass numbers:

• C/E — C major with E in the bass (first inversion)
• C/G — second inversion

Secondary dominants are dominant 7 chords that resolve to a chord other than the I. They’re written with a slash too:

• V/V (read “five of five”) — the dominant of the V chord. In C major, V = G, so V/V = D7 (the V of G).
• V/ii — the dominant of ii. In C major, ii = Dm, so V/ii = A7.

You’ll see these in nearly every Beatles song. The chord that’s “out of the key” but sounds amazing is almost always a secondary dominant.

A worked analysis

Take “Heart and Soul” (or “Stand By Me”, “Earth Angel”…):

C - Am - F - G - C

Analysis: I - vi - IV - V - I.

This pattern lives in every key the same way: - In G: G - Em - C - D - G - In E♭: E♭ - Cm - A♭ - B♭ - E♭

Memorise the Roman numerals and you’ve memorised the song in all 12 keys at once.

Try this

Pick any pop song you know the chords to. Convert them to Roman numerals. (If you’re unsure of the key, the first chord is usually I; the chord the song “rests” on is usually I.) Then play the same progression in a different key by translating the numerals back to chords.

You just transposed a song without a chord chart. This is what good musicians do every time someone asks “can you do that in B♭?”