The song's backbone
A chord progression is simply the order chords move in through a song. It sets the emotional journey underneath the melody — tension and release, home and away — and gives a song its structure.
Why a few go a long way
A surprising amount of popular music runs on a handful of common progressions. Because certain chord movements sound satisfying to our ears, the same patterns recur across decades and genres, often with just four chords.
Naming a chord by where it sits in the key
Roman-numeral analysis is the standard way theorists describe a progression’s relationship to its home key rather than any one set of note names. Per the open textbook Fundamentals (Samuel Brady and Kris Shaffer), “uppercase Roman numerals denote major triads, and lowercase Roman numerals denote minor triads,” with a raised “o” marking a diminished triad and a “+” marking an augmented one. The number itself — I through vii — is just the scale degree the chord is built on, 1 through 7.
In a major key those seven numerals come with fixed, non-optional qualities: I, IV and V are major; ii, iii and vi are minor; vii is diminished (vii°). Nobody chooses that pattern per song — it falls straight out of stacking the major scale’s own notes in thirds, so a major-key progression is really a sequence of picks from the same seven fixed chords, plus whatever a writer deliberately borrows from outside them.
What changes in a minor key
The same source’s table shows the pattern shifting for a minor key: i is minor, ii is diminished (ii°), III is major, iv is minor, v is minor (or raised to V, a major chord, for a stronger pull to the tonic), VI is major, and VII is major (or vii°, depending on convention). A Roman numeral therefore encodes three things at once — the chord’s root as a scale degree, its quality, and, when figured-bass numbers are added, its inversion.
That is also why the same numerals transposed into two different keys sound related rather than identical: the quality pattern travels with the key, but the actual pitches do not. A I-V-vi-IV progression in any major key uses exactly the same four qualities in exactly the same order — major, major, minor, major — which is a real part of why different songs built on it can still feel like variations of one shape.
In C major the seven stock chords read out as I=C, ii=Dm, iii=Em, IV=F, V=G, vi=Am, vii°=Bdim. Swap to G major and the qualities stay identical in the same order — I=G, ii=Am, iii=Bm, IV=C, V=D, vi=Em, vii°=F♯dim — only the letter names move.
Getting started
- Learn the basic chords in a key first.
- Try common progressions and hear how they feel.
- Notice the home chord and how others pull back to it.
- Swap chords in and out to change the mood.
Turn a numeral progression into chord names
Pick a major key and a common progression, and this applies the fixed quality table above to name the actual chords. Nothing is stored or sent anywhere.
Qualities (major/minor) are fixed by the key per the roman-numeral table below; only the letter names change from key to key.
Where this comes from
Samuel Brady and Kris Shaffer, Fundamentals (Open Music Theory), “Roman Numerals and SATB Chord Construction,” University of Nebraska Pressbooks: uppercase/lowercase for major/minor triads, the “o” and “+” modifiers, and the fixed major- and minor-key quality tables. pressbooks.nebraska.edu · accessed 4 August 2026.
The worked C-major and G-major chord lists, and the calculator’s chord-naming arithmetic, are this page’s own application of that quality table to specific keys — not themselves stated in the source.
Common questions
Why do so many songs sound similar?
Many share a few common, satisfying chord progressions. The melody and arrangement make them feel different.
How many chords do I need?
You can write countless songs with just three or four basic chords in a key.
What makes a progression sound good?
Movement between tension and resolution — chords that pull away from the home chord and then back to it.