::Roman numeral analysis
In music, Roman numeral analysis involves the use of Roman numerals to represent chords. In this context, Roman numerals (I, II, III, IV, ...) typically denote scale degrees (first, second, third, fourth, ...). When a Roman numeral is used to represent a chord, it is meant to indicate the scale degree corresponding to its root note, which is the note on which the chord is built. For instance, III is the Roman numeral which denotes either the third degree of a scale, or the chord built on that degree. In many cases, uppercase Roman numerals (such as I, IV, V) represent major chords while lowercase Roman numerals (such as i, iv, v) represent the minor chords (see Major and Minor below for alternative notations); elsewhere, upper-case Roman numerals are used for all chords.<ref name=roger>Sessions, Roger (1951). Harmonic Practice. New York: Harcourt, Brace. LCCN 51008476. p. 7.</ref>
In the most common day-to-day use, Roman numerals allow musicians to quickly understand the progression of chords in a piece. For instance, the standard twelve bar blues progression is denoted by the Roman numerals I7 (first), IV7 (fourth), and V7 (fifth). In the key of C (where the notes of the scale are C, D, E, F, G, A, B), the first scale degree (Tonic) is C, the fourth (Subdominant) is F, and the fifth (Dominant) is a G. So the I7, IV7, and V7 chords are C7, F7, and G7. Similarly, if one were to play the same progression in the key of A (A, B, C♯, D, E, F♯, G♯) the I7, IV7, and V7 chords would be A7, D7, and E7. In essence, Roman numerals provide a way to abstract chord progressions, by making them independent of the selected key. This allows chord progressions to be easily transposed to any key.
Roman numeral analysis sections
Intro Overview Common practice numerals Jazz and pop numerals Sources
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