Derive chords from the spelled scale
Write the scale first, preserving one letter per diatonic degree. Build a triad on each degree by selecting that note, skipping one scale note, selecting the next, skipping again and selecting the fifth. In C major, degree two selects D, F and A, so ii is D minor; degree seven selects B, D and F, so vii° is B diminished.
This method is safer than shifting memorised piano shapes because the scale already contains the key’s required accidentals. In D major, the same degree-two stack is E–G–B, while degree seven is C♯–E–G. The Roman-numeral pattern remains comparable even though every absolute root changes.
Major-key triads and sevenths
Major-key triads follow I major, ii minor, iii minor, IV major, V major, vi minor and vii° diminished. Adding one more alternate scale note produces Imaj7, ii7, iii7, IVmaj7, V7, vi7 and viiø7. The dominant seventh is unique within the unaltered major collection because it combines a major triad with a minor seventh.
In C major, V7 is G–B–D–F and viiø7 is B–D–F–A. The third and seventh of G7, B and F, form a tritone whose contrary resolution helps explain the dominant-to-tonic pull without requiring a copyrighted repertoire example.
Minor-key choices must state the scale form
Natural minor triads follow i, ii°, III, iv, v, VI and VII. Tonal minor practice often raises degree seven, changing v to V and VII to vii° so the dominant contains a leading tone. A single table must therefore say whether it is derived from natural, harmonic or melodic minor rather than labelling all possibilities simply “minor”.
In A natural minor, v is E–G–B. With G raised to G♯, E–G♯–B becomes a major dominant and E7 adds D. The altered note is not in the natural-minor signature; it is a contextual accidental used by the harmonic form.
Roman-numeral grammar
The numeral gives scale degree; uppercase indicates major-type quality, lowercase minor, ° diminished and ø half-diminished. Accidentals before a numeral alter its root relative to the key. Inversion figures may be added only when their meaning is explained: 6 commonly marks a triad in first inversion, 6/4 second inversion, 6/5 a seventh chord in first inversion, 4/3 second and 4/2 third.
Roman numerals make transposition visible. I–vi–IV–V maps to C–Am–F–G in C major and G–Em–C–D in G major. The relationship stays fixed while the key-aware note spellings and keyboard positions change.
Four cadence families
An authentic cadence ends V–I or V7–I; a half cadence stops on V; a plagal cadence moves IV–I; a deceptive cadence moves V to a chord other than I, commonly vi in major. These labels describe harmonic arrival and must be considered with phrase position, melody and voice leading rather than inferred from two isolated chord symbols alone.
In C major, the bass examples G–C, any chord–G, F–C and G–A illustrate those four categories. In D major they transpose to A–D, any chord–A, G–D and A–B. Generated playback can compare the bass motion while the text keeps the functional numerals explicit.
Primary chords, circle neighbours and transposition
I, IV and V are the primary major-key triads. The circle places IV anticlockwise and V clockwise from I: for D major, G lies anticlockwise and A clockwise. That visual relationship supports key navigation, while the chords-in-key tool supplies the complete seven-chord collection.
To transpose ii–V–I from C to E♭ major, retain degrees two, five and one. The result is F minor, B♭ major and E♭ major, spelled F–A♭–C; B♭–D–F; and E♭–G–B♭. The Roman numerals carry the structure; the target scale supplies the letters and accidentals.
A bounded analysis workflow
State the key and scale form, spell its notes, derive the chord tones, then assign numeral, quality and inversion from the bass. Mark any chromatic note that falls outside the chosen collection instead of forcing it into a diatonic label. Finish by checking whether a cadence name is supported by phrase function, not merely by the last two roots.
ChordMetric provides generated examples and neutral progressions only. It does not attach common harmonic patterns to named songs, lyrics, scores or recordings.