Roman numeral analysis

In music theory, Roman numeral analysis is a type of harmonic analysis in which chords are represented by Roman numerals, which encode the chord's degree and harmonic function within a given musical key.

Specific notation conventions vary: some theorists use uppercase numerals (e.g. I, IV, V) to represent major chords, and lowercase numerals (e.g. ii, iii, vi) to represent minor chords. Others use uppercase numerals for all chords regardless of their quality.^[2]

Roman numerals can be used to notate and analyze the harmonic progression of a composition independent of its specific key. For example, the ubiquitous twelve-bar blues progression uses the tonic (I), subdominant IV, and dominant (V) chords built upon the first, fourth and fifth scale degrees respectively.

E^maj7 becomes I^maj7 (also I^∆7, or simply I)

F♯m⁷ becomes II^m7 (also II⁻⁷, II^min7, IIm, or II⁻)

G♯m⁷ becomes III^m7 (also III⁻⁷, III^min7, IIIm, or III⁻)

A^maj7 becomes IV^maj7 (also IV^∆7, or simply IV)

B⁷ becomes V⁷ (or simply V; often V⁹ or V¹³ in a jazz context)

C♯m⁷ becomes VI^m7 (also VI⁻⁷, VI^min7, VIm, or VI⁻)

D♯^ø7 becomes VII^ø7 (also VII^m7b5, VII^-7b5, or VII^ø)

In music theory, fake books and lead sheets aimed towards jazz and popular music, many tunes and songs are written in a key, and as such for all chords, a letter name and symbols are given for all triads (e.g., C, G⁷, Dm, etc.). In some fake books and lead sheets, all triads may be represented by upper case numerals, followed by a symbol to indicate if it is not a major chord (e.g. "m" for minor or "^ø" for half-diminished or "7" for a seventh chord). An upper case numeral that is not followed by a symbol is understood as a major chord. The use of Roman numerals enables the rhythm section performers to play the song in any key requested by the bandleader or lead singer. The accompaniment performers translate the Roman numerals to the specific chords that would be used in a given key.

In the key of E major, the diatonic chords are:

In popular music and rock music, "borrowing" of chords from the parallel minor of a major key is commonly done. As such, in these genres, in the key of E major, chords such as D major (or ♭VII), G major (♭III) and C major (♭VI) are commonly used. These chords are all borrowed from the key of E minor. Similarly, in minor keys, chords from the parallel major may also be "borrowed". For example, in E minor, the diatonic chord built on the fourth scale degree is IVm, or A minor. However, in practice, many songs in E minor will use IV (A major), which is borrowed from the key of E major. Borrowing from the parallel major in a minor key, however, is much less common.

Using the V7 or V chord (V dominant 7, or V major) is typical of most jazz and pop music regardless of whether the key is major or minor. Though the V chord is not diatonic to a minor scale, using it in a minor key is not usually considered "borrowing," given its prevalence in these styles.

Diatonic scales[edit]

Major scale[edit]

The table below shows the Roman numerals for chords built on the major scale.