"Roman Numeral Analysis" is a system used in music theory to represent the chords and their relationships within a musical composition. It provides a way to analyze and understand the harmonic structure of a piece of music, regardless of its key. Roman numerals are employed to denote the scale degree on which a chord is built and to indicate whether the chord is major, minor, diminished, or augmented. Here's a breakdown of how Roman numeral analysis works:
- Determining the Key: Before performing Roman numeral analysis, it's essential to determine the key of the composition. The key signature (sharps or flats at the beginning of the musical staff) and the tonic note (the note that feels like the "home" note) are crucial in identifying the key.
- Assigning Roman Numerals: Once the key is established, Roman numerals are assigned to each degree of the diatonic scale. The primary diatonic chords in a major key are typically represented as follows:
- I: Represents the tonic chord (major).
- ii: Represents the supertonic chord (minor).
- iii: Represents the mediant chord (minor).
- IV: Represents the subdominant chord (major).
- V: Represents the dominant chord (major).
- vi: Represents the submediant chord (minor).
- vii°: Represents the leading-tone chord (diminished).
- In a minor key, the chords may vary slightly, depending on whether it's the natural minor, harmonic minor, or melodic minor scale being used.
- Analyzing Chord Progressions: Roman numerals are then used to represent the chords within a composition. By analyzing the progression of Roman numerals, one can understand the harmonic structure of the piece, including chord changes and modulations to different keys if they occur.
- Distinguishing Chord Quality: Capital Roman numerals (I, IV, V) usually represent major chords, while lowercase Roman numerals (ii, iii, vi) represent minor chords. The diminished chord is represented by a lowercase Roman numeral with a ° symbol (vii°).
- Extensions and Alterations: Roman numeral analysis can also include chord extensions and alterations. For example, a "V7" indicates a dominant seventh chord, while "IVmaj7" represents a major seventh chord built on the subdominant degree.
- Functional Analysis: Beyond identifying chords, Roman numeral analysis can reveal the functional relationships between chords, such as tonic-dominant (I-V) progressions, which create tension and resolution.
Roman numeral analysis is a valuable tool for musicians, composers, and music theorists to study and communicate the harmonic aspects of music. It aids in understanding the underlying structure of a piece and provides a common language for discussing chord progressions and harmonic patterns.