Explaining Roman Numeral Analysis in Music Theory

Functional harmony describes the roles chords play in a progression. The tonic chord (number 1) provides a sense of home and rest, representing stability. The dominant chord (number 5) creates tension that naturally resolves back to the tonic. Predominant or subdominant chords (numbers 2 and 4) typically lead to dominant chords. This three-category system explains how progressions create tension and release. Most simple progressions follow tonic-dominant-tonic patterns, while more complex ones may use tonic-subdominant-dominant-tonic sequences.

In major keys, chords are categorized by function: tonic (I, III, VI) share two notes with the tonic triad and provide stability; predominant (II, IV) prepare the dominant; dominant (V, VII) contain the leading tone creating tension. This functional system explains why certain chords naturally precede others. The I-IV-V-I progression exemplifies this, moving from tonic to predominant to dominant to tonic, creating natural harmonic motion. Understanding these relationships allows prediction of chord behavior and facilitates composition and improvisation.

Functional harmonic analysis categorizes chords into three types based on their resolution tendencies: Predominant chords pull toward dominant chords, Dominant chords pull toward tonic chords, and Tonic chords are stable and do not pull toward other chords. The ii-V-I (251) cadence serves as the fundamental building block of tonal jazz harmony, appearing throughout jazz standards. Functional progressions generally move from tonic to predominant to dominant, with the option to stop at dominant (incomplete cadence) or return to tonic (complete cadence). Tonic prolongation refers to chords that extend the tonic function without creating a complete cadence, including chord substitutions and quick passing chords lasting no more than half a bar.

Functional harmony divides scale degrees into three groups: tonic (I), predominant (IV), and dominant (V). The tonic represents peace and homeostasis - all needs met, nothing threatening. The dominant represents joyful expectation, containing strong direction pointing toward the tonic. The predominant (IV) is emotionally deep, creating feelings of newness and freshness while remaining heartwarming and comforting.

Functional harmony describes how chords behave in a sequence, similar to grammatical structures. The tonic chord (I) has tonic function—it feels like home and represents rest. The subdominant chord (IV) has subdominant or predominant function—it creates motion away from home. The dominant chord (V) has dominant function—it asks to be resolved back home to the tonic. These functions determine how chords relate to each other within a key center.

In music theory for songwriters, borrowed chords are chords taken from the parallel minor key (sharing the same tonic) that add harmonic color to major key compositions, such as the flat third major chord (C major in A major) and flat sixth/fifth major chords (F major and G major in A major); secondary dominant chords are dominant seventh chords that lead to other chords in the key (like F#7 leading to Bm or C#7 leading to F#m), creating tension and resolution that enhances songwriting by providing common progressions like I to flat three major to four major to four minor, which features the powerful leading tone effect where the third of the borrowed chord resolves up a half step to the fourth chord.

Advanced chord progressions use sophisticated harmonic devices to create interest. Secondary dominant chords temporarily function as the dominant of a different key, creating tension that resolves elsewhere. Borrowed chords, taken from parallel minor keys, add color and were commonly used by The Beatles. Chromatic mediant modulation involves borrowing chords from keys a third away, creating sophisticated harmonic movement. These techniques allow songwriters to move beyond the standard one-four-five-six progression while maintaining musical coherence.

This section establishes the theoretical foundation for chromatic harmony. Diatonic music restricts itself to the notes of a specific major or minor scale, while chromatic music makes all 12 notes available, representing the highest resolution of pitch organization. A dominant chord is defined as a major triad topped with a minor seventh, creating instability through the tritone between third and seventh. Secondary dominants are created by transforming any diatonic chord into a dominant chord (adding a seventh), creating strong expectation that the next chord will be the one a fifth below. Using the cycle of fifths, every chord can be transformed to create the next secondary dominant, creating a solar system-like structure where each degree has a 'moon' orbiting around it.

To modulate to a parallel minor key, use a dominant seventh chord that belongs to the new key. For example, to modulate from F major to F minor, use D7 (the dominant of G) which resolves to G major, then use Eb7 (the dominant of F minor) to resolve to F minor. The modulation point is where the dominant seventh of the new key appears. A dominant seventh chord can serve as a bridge between keys. To modulate, create a dominant seventh chord that belongs to the new key. For example, to modulate from F major to G minor, use D7 (the dominant of G) which resolves to G minor. A backdoor dominant can be used for modulation. For example, to modulate from G minor to F minor, use E7 (the dominant of A) which resolves to A major, then use Eb7 (the dominant of F minor) to resolve to F minor. Borrowed chords are chords taken from parallel keys or related keys. For example, in G minor, A major (the major of the parallel major) can be borrowed.

Roman numerals (I, V, vi, IV) represent chord degrees within a key, enabling description of progressions independent of specific keys. The I-V-vi-IV progression is fundamental to popular music, forming the harmonic skeleton of countless songs including 'Let It Be' by The Beatles. This progression consists of three major chords (I, V, IV) and one minor chord (vi). To transpose a progression to a new key, apply the same Roman numeral pattern: C major's I-V-vi-IV (C-G-Am-F) becomes G major's G-D-Em-C. This works because harmonic function remains consistent regardless of key.

Roman numerals analyze chord function: uppercase (I, IV, V) indicates major chords, lowercase (ii, iii, vi) indicates minor chords, vii° indicates diminished. This abstraction allows understanding harmonic function independent of specific key. The progression I-IV-V-I is the same harmonic function in any key. The hierarchy of harmonic function (tonic, subdominant, dominant) creates the emotional structure of Western music, with tension and resolution driving musical interest.

Music theory provides vocabulary to describe musical effects that people love. Harmony is the largest component of music's color and texture. Roman numeral analysis shows the outline of harmony visually. A piece has a key (tonal center), with the tonic represented by Roman numeral one. Harmony has two dimensions: vertical (notes played simultaneously) and horizontal (chord changes). A cadence is a chord change that resolves, with the perfect cadence (5-1) meaning 'completely finished' in Latin. Roman numerals show movement while figures show harmonic detail.

Roman numeral analysis is a notation system for documenting musical progressions. Major chords use uppercase Roman numerals (I, IV, V), minor chords use lowercase (ii, iii, vi), and diminished chords are marked with a circle or asterisk. This system allows musicians to understand chord function and structure. The video demonstrates analyzing progressions in both major and minor keys, showing how the same chord sequence creates different emotional effects depending on the key.

This section covers two approaches to writing minor key chord progressions in Roman numerals. The first method relates chords to the major scale, using flat symbols (flat 3, flat 7) to indicate natural notes. The second method relates directly to the minor key, using simple numerals (3, 7) without flats. The practical approach for chord charts is to use Roman numerals relative to the major scale regardless of tonality, avoiding ambiguity when songs modulate between major and minor keys. This ensures players can understand and perform the song without confusion about whether symbols refer to sharp or natural notes.