Análise por Cifra Romana

Roman numeral analysis, chord function in any key

Roman numeral analysis is a music-theory notation in which each chord is labelled by the scale degree of its root rather than its letter name. Because the numerals describe a relationship inside the key, the same analysis transposes instantly: I-V-vi-IV is the same progression whether you play it in C, in G or in Eb. The conventions are tight and worth memorising. Uppercase numerals — I, IV, V — are major triads. Lowercase numerals — ii, iii, vi — are minor triads. A ° sign marks a diminished chord (vii° in any major key), and a + marks an augmented chord.

Plotted on the diatonic seven, C major reads I = C, ii = Dm, iii = Em, IV = F, V = G, vi = Am, vii° = B°. The parallel A natural minor reads i = Am, ii° = B°, III = C, iv = Dm, v = Em, VI = F, VII = G — note the uppercase III, VI and VII because those triads are major. In practice composers raise the seventh in minor to obtain a true leading tone, turning v into V (or V7) for an authentic cadence. Inversions ride on figured-bass numbers: I⁶ is the first inversion (third in the bass), I⁶/₄ is the second inversion (fifth in the bass), and V⁷ is a dominant seventh. Secondary dominants use a slash: V⁷/V ("five seven of five") is the dominant of the dominant — D7 in C major, resolving to G.

Why bother: songwriting, transposition, ear training

The numerals let you see structure that letter names hide. Once a song is reduced to I-V-vi-IV you spot the same shape in Don't Stop Believing, Let It Be, With or Without You, No Woman No Cry and dozens of others — the Axis of Awesome medley. Jazz students drill ii-V-I in every key because almost every standard is a chain of ii-V-I modulations. The 50s doo-wop sound is I-vi-ii-V or I-vi-IV-V. Roman analysis is also the fastest way to transpose: turn the chart into numerals, pick the new tonic, expand. Singers do this on stage every night when a key change is requested.

Origin: figured bass to Gottfried Weber

The system descends from Baroque figured bass, where a bass note plus numbers under it specified the harmony above. The German theorist Gottfried Weber formalised Roman numerals between 1817 and 1821 in Versuch einer geordneten Theorie der Tonsetzkunst. Hugo Riemann's late-19th-century function theory classified the degrees into tonic, subdominant and dominant families, and Heinrich Schenker's structural analysis treated long passages as elaborations of a single I-V-I. Modern Berklee notation extends Roman numerals with parenthetical alterations such as V7alt or V7(b9) for jazz voicings. Software-side, MuseScore, Sibelius and Dorico let you type Roman analyses under the staff; Logic Pro and many DAWs convert chord-symbol tracks to numerals on demand.

FAQ

What is the difference between i and I? Case carries quality. Lowercase i is a minor triad on the first degree (Am in A minor); uppercase I is a major triad (A in A major). The same letter therefore describes opposite chord qualities depending on the case — there is no other way to read it.

Does Roman analysis replace chord symbols? No — it complements them. Chord symbols (C, Am7, F/A) tell a player what to grab on the fretboard. Roman numerals tell an analyst what role each chord plays in the key. Lead sheets carry both layers when teaching or arranging.

Can I transpose a song with the numerals alone? Yes, that is the main practical payoff. Convert the chart into numerals once, then expand into any new key by reading the scale of the new tonic. Most worship-band charts and Nashville-number-system charts use this exact workflow.

How are minor-key numerals different? The diatonic triads in minor produce uppercase III, VI, VII (major) and lowercase i, iv, v with ii°. Because the natural minor lacks a leading tone, classical practice raises the seventh and writes V or V7 instead of v for an authentic cadence; harmonic and melodic minor scales formalise that adjustment.