What does I-V-vi-IV actually mean?

The Roman numerals are scale degrees: I is a chord built on the first note of the key, V on the fifth, and so on. Upper-case numerals are major chords and lower-case are minor. In C major, I-V-vi-IV is C, G, Am, F. The power of the notation is that it is key-independent: the same numerals name the same progression in G major (G, D, Em, C) or any other key.

How do I transpose a progression to another key?

Keep the Roman numeral pattern and change the key centre. Each chord keeps its degree and quality but its root moves by the same distance as the tonic. If C, G, Am, F is too low for a singer, moving the key centre up two semitones to D gives D, A, Bm, G: the identical progression, just higher. Capo users do the same thing mechanically by keeping the shapes and moving the capo.

Why does a major key contain minor chords?

Diatonic chords are built by stacking every second note of the scale, and the gaps between scale notes are uneven. Stacking from the first, fourth and fifth degrees of a major scale happens to produce major triads, stacking from the second, third and sixth produces minor triads, and the seventh degree yields a diminished triad. That is why C major contains Dm, Em and Am: the minor chords are baked into the scale itself.

Chord Progression Generator

This chord progression generator turns a key and a classic pattern into a ready-to-play set of chords. Choose your key centre, pick a progression such as the pop anthem I-V-vi-IV, the 50s doo-wop I-vi-IV-V, the jazz ii-V-I or a full 12-bar blues, and the generator names every chord in order, shows the pattern in Roman numerals and lists the complete set of diatonic chords for the key so you can experiment with substitutions. Each pattern is a fixed recipe of scale degrees, so the result is deterministic: the same key and pattern always give the same chords, which makes it easy to transpose a song for a singer or shift a riff into a friendlier guitar key. Songwriters use it to sketch a verse or chorus quickly, beginners use it to see why so many hit songs share the same four chords, and teachers use it to demonstrate how Roman numeral notation works across keys. Minor-key patterns are included too, from the natural minor i-iv-v to the Andalusian run that walks down to a major V chord. Pair it with our chord finder if you want to see the individual notes inside each chord the generator hands you, and use one chord per bar as a starting point.

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Key centre (tonic)

Progression pattern

C - G - Am - F

I-V-vi-IV in C major

KeyC major

PatternPop anthem

Chords in the loop4

Play one chord per bar and loop it. In C major the pattern I-V-vi-IV gives you C, G, Am and F.

Diatonic chords in C major: C, Dm, Em, F, G, Am, Bdim.

Upper-case numerals are major chords, lower-case are minor and dim marks a diminished chord. The Andalusian pattern ends on a major V borrowed from the harmonic minor, which is standard practice. One chord per bar is a starting point, not a rule.

How it works

Roman numeral notation describes a progression by scale degree instead of by note name, which makes it portable between keys. The generator takes your key centre as degree one, then walks up the scale to find the root of each numbered chord: degree V sits 7 semitones above the tonic, degree vi sits 9 semitones up, and so on. Chord quality comes with the degree: in a major key, degrees I, IV and V carry major triads, ii, iii and vi carry minor triads, and vii carries a diminished triad, because that is what stacking scale notes in thirds produces. Minor-key patterns use the natural minor spelling, where III, VI and VII are major chords sitting 3, 8 and 10 semitones above the tonic, and the Andalusian pattern swaps in the harmonic minor's major V for its final chord. Each chord root is spelled by letter so that flat keys stay in flats and sharp keys stay in sharps.

Worked example

Keep the defaults: key centre C with the pop anthem pattern I-V-vi-IV. Degree I is the tonic chord C, degree V sits 7 semitones up on G, degree vi sits 9 semitones up and is minor, giving Am, and degree IV sits 5 semitones up on F, so the loop is C, G, Am, F. Move the key centre to G and the same pattern becomes G, D, Em, C: an identical shape from a new starting point, which is all transposition is. Switch to the Andalusian pattern in the key of A and you get Am, G, F, E, a minor-key walk-down where the final E major chord pulls the ear back to Am.

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