Roman numeral analysis

Roman numeral analysis numbers chords by their place in the key. The home chord, built on the tonic, is I (or i in a minor key). The chord built on the second note of the scale is ii, and so on up to vii°. The numbers describe position, so a progression written in numerals works in any key.

The chords of C major and A minor

C major and A minor share seven notes, so they share seven chords. Only the numbers change, because each key counts from its own home note.

The case of the numeral tells you the chord’s quality, so vii° is diminished in every major key. A 7 after it adds a seventh, so V7 in C major is G7. Songs in A minor often raise G to G#, which turns v into V (E major) for a stronger pull home.

Why musicians count in numbers

A progression keeps its numbers in every key. I V vi IV is C G Am F in C major and G D Em C in G major. That is how musicians can say “a I IV V song” and mean something exact. The 1-5-6-4 Chord Progression covers I V vi IV and why it works.

Session players in Nashville write the same idea with ordinary numbers: 1, 4, 5, and 6- or 6m for the minor chord on the 6th step. Their chart system, the Nashville Number System, took shape in the late 1950s.

In Gelato Synth, Chords mode labels every pad with its Roman numeral and chord name. On the Triad setting, with C as the root and Major as the scale, the pads read the C major column above, plus the I an octave up. To work out the numerals for any key, read How to Find Chords in a Key.