Roman Numerals & Cadences

Lead-sheet symbols (C, Gm…) tell you which chord, but not what role that chord plays in the key. Roman numerals fill that gap: they number chords by the scale degree they are built on, revealing patterns shared across many pieces in different keys.

How do Roman numerals work?

Roman numerals number a chord by the scale degree it's built on, within a specified key. Roman numerals represent chords within a specified key. The quality conventions are:

• Uppercase (I, IV, V) = a major chord.
• Lowercase (ii, iii, vi) = a minor chord.
• Lowercase with ° (vii°) = a diminished chord.
• Uppercase with + (III+) = an augmented chord.

"I" is the chord built on scale degree 1 (the tonic). Because it depends on the key, a Roman numeral analysis always names the key (e.g. "C: I").

What are the diatonic chords in major?

Building a triad on each degree of the major scale always yields the same seven-chord pattern of qualities. Diatonic means using only the notes in the key signature. Building a triad on each degree of the major scale always yields the same pattern of qualities: M–m–m–M–M–m–° (verified with tonal).

Why does minor have more than seven chords?

Because minor has three scale forms (natural, harmonic, melodic), the 6th and 7th degrees shift and give you more options than seven. Because minor has three scale forms, the changing 6th and 7th degrees produce more than seven chords. In practice, the most common chords in minor (using A minor) are:

Both VII (built on the lowered 7th of natural minor — the subtonic) and vii° (built on the raised 7th — the leading tone) are common: VII appears in circle-of-fifths progressions and rock/pop, while vii° is usually a passing harmony or has dominant function.

What are the cadence types?

There are four basic cadences — authentic, plagal, deceptive, and half — each a chord pair that gives the ear a sense of arrival. A cadence is a harmonic point of arrival — like a comma or period in written language, giving the ear a moment to rest. There are four basic cadences:

The plagal cadence is also called the "Amen cadence" for its use at the end of hymns. A deceptive cadence means V does not go to I as the ear expects — the most common realization is V → vi.

See Triads to review chord qualities, and Seventh Chords plus Harmonic Progression & Function for the next steps.

Frequently asked questions

Why does a Roman numeral analysis always name the key? Because Roman numerals show scale degree, not an absolute chord. "I" is C in C major but G in G major, so the key has to be stated (e.g. "C: I").

What's a deceptive cadence? It's when V does not resolve to I as the ear expects. The most common realization is V → vi, steering the harmony somewhere unexpected.

How do the two chords on minor's 7th degree differ? VII is built on the lowered 7th (the subtonic) of natural minor and shows up in circle-of-fifths progressions; vii° is built on the raised 7th (the leading tone) of harmonic minor and usually has dominant function or acts as passing harmony.