Roman numeral analysis is a type of musical analysis in which chords are represented by Roman numerals . In some cases, Roman numerals denote scale degrees themselves. More commonly, however, they represent the chord whose root note is that scale degree. For instance, III denotes either the third scale degree or, more commonly, the chord built on it. Typically, uppercase Roman numerals are used to represent major chords, while lowercase Roman numerals are used to represent minor chords. However, some music theorists use upper-case Roman numerals for all chords, regardless of chord quality. In Western classical music in the 2000s, music students and theorists use Roman numeral analysis to analyze the harmony of a composition. In pop, rock, traditional music, and jazz and blues, Roman numerals can be used to notate the chord progression of a song independent of key. For instance, the standard twelve-bar blues progression uses the chords I, IV, V, sometimes written I7, IV7, V7, since they are often dominant seventh chords. In the key of C major, the first scale degree is C, the fourth is F, and the fifth is a G. So the I7, IV7, and V7 chords are C7, F7, and G7. On the other hand, in the key of A major, the I7, IV7, and V7 chords would be A7, D7, and E7. Roman numerals thus abstract chord progressions, making them independent of key, so they can easily be transposed.
History
Roman numeral analysis is based on the idea that chords can be represented and named by one of their notes, their root. The system came about initially from the work and writings of Rameau’s fundamental bass. Arabic numerals have been used in the 18th century for the purpose of denoting the fundamental bass, but that aspect will not be considered here. The earliest usage of Roman numerals may be found in the first volume of Johann Kirnberger's Die Kunst des reinen Satzes in 1774. Soon after, Abbé Georg Joseph Vogler occasionally employed Roman numerals in his Grunde der Kuhrpfälzischen Tonschule in 1778. He mentioned them also in his Handbuch zur Harmonielehre of 1802 and employed Roman numeral analysis in several publications from 1806 onwards. Gottfried Weber's Versuch einer geordneten Theorie der Tonsetzkunst is often credited with popularizing the method. More precisely, he introduced the usage of large capital numerals for major chords, small capitals for minor, superscript o for diminished 5ths and dashed 7 for major sevenths – see hereby. Simon Sechter, considered the founder of the Viennese "Theory of the degrees", made only a limited use of Roman numerals, always as capital letters, and often marked the fundamentals with letter notation or with Arabic numbers. Anton Bruckner, who transmitted the theory to Schœnberg and Schenker, apparently did not use Roman numerals in his classes in Vienna.
Common practice numerals
In music theory related to or derived from the common practice period, Roman numerals are frequently used to designate scale degrees as well as the chords built on them. In some contexts, however, arabic numerals with carets are used to designate the scale degrees themselves . The basic Roman numeral analysis symbols commonly used in pedagogical texts are shown in the table below. The Roman numerals for the seven root-position diatonic triads built on the notes of the C major scale are shown below.
In addition, according to Music: In Theory and Practice, "ometimes it is necessary to indicate sharps, flats, or naturals above the bass note." The accidentals may be below the superscript and subscript number, before the superscript and subscript number, or using a slash or plus sign to indicate that the interval is raised of the degrees in bars 13–15 of the Allegro assai of J. S. Bach's Sonata in C major for violin solo, BWV 1005.
Inversions
Roman numerals are sometimes complemented by Arabic numerals to denote inversion of the chords. The system is similar to that of Figured bass, the Arabic numerals describing the characteristic interval above the bass note of the chord, the figures 3 and 5 usually being omitted. The first inversion is denoted by the numeral 6, even although a complete figuring should require ; the numerals denotes the second inversion. Inverted seventh chords are similarly denoted by one or two Arabic numerals describing the most characteristic intervals, namely the interval of a second between the 7th and the root: V7 is the dominant 7th ; V is its first inversion ; V its second inversion ; and V or V2 its third inversion.
Jazz and pop numerals
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. 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. 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:
Emaj7 becomes Imaj7
Fm7 becomes ii7
Gm7 becomes iii7
Amaj7 becomes IVmaj7
B7 becomes V7
Cm7 becomes vi7
Dø7 becomes viiø7
In popular music and rock music, "borrowing" of chords from the tonic minor of a key into the tonic major and vice versa is commonly done. As such, in these genres, in the key of E major, chords such as D major, G major and C major are commonly used. These chords are all borrowed from the key of E minor. Similarly, in minor keys, chords from the tonic major may also be "borrowed". For example, in E minor, the diatonic chords for the iv and v chord would be A minor and B minor; in practice, many songs in E minor will use IV and V chords, which are "borrowed" from the key of E major.
Diatonic scales
[|Major] scale
The table below shows the Roman numerals for chords built on the major scale. In the key of C major, these chords are
[|Minor] scale
The table below shows the Roman numerals for the chords built on the natural minor scale. In the key of C minor, these chords are
The seventh scale degree is often raised to a leading tone making the dominant chord a major chord and the subtonic chord a diminished chord. This is called the harmonic minor scale.
