Someone picks up a guitar and starts playing. You recognise one song, then another, then a third. Their hands barely seem to change position. It feels as though they have found a shortcut through your entire music collection.
Many pop songs share four-chord patterns because those patterns provide a familiar, adaptable foundation for a melody. Songwriters can keep the harmony simple while changing the rhythm, lyrics, performance and arrangement. Reusing the foundation still leaves a remarkable amount of room to create.
One of the best-known sequences is I–V–vi–IV. In C major, that means C major, G major, A minor and F major, usually written C–G–Am–F. A chord progression is simply a sequence of chords. Here, the Roman numerals identify chords built on the first, fifth, sixth and fourth notes of the major scale; the lowercase vi indicates a minor chord.
The pattern can move into another key. In G major, it becomes G–D–Em–C. The pitches change, but the relationships between the chords stay the same.
Berklee Online lists U2’s “With or Without You,” Jason Mraz’s “I’m Yours” and The Beatles’ “Let It Be” among familiar examples of this progression. You can hear why a chord list tells only part of the story: those recordings have different melodies, vocal personalities and arrangements.
The comedy band The Axis of Awesome made this connection the basis of “Four Chords,” threading excerpts from numerous songs over a repeating accompaniment. Music theorist Mark Richards later used the name “Axis progressions” for this family of related chord patterns.
A medley is an illustration, though. A passage that fits the shared accompaniment does not tell you every chord in the original recording. Songs can change direction in another section, add passing chords or vary the pattern. Recognising a common ingredient is only the beginning of comparing the recipes.
There is a practical reason these chords work together: all four can be built from notes in the same major scale. In our C-major example, no note outside C, D, E, F, G, A and B is needed. Moving between major and minor chords gives the sequence contrast within that shared collection.
The pattern also works as a loop. Open Music Theory describes recurring chord sequences as a normal feature of pop and rock, appearing in verses, choruses and other sections. Returning to the same sequence gives a singer repeated opportunities to place a new phrase over familiar harmony.
This helps explain the usefulness of a simple accompaniment. A line can begin before the next chord arrives, stretch across the change or leave a gap for the instruments. A chorus can introduce a new vocal idea while the accompaniment keeps going. The musical interest can move between different parts of the performance.
Even the starting point matters. Rotate C–G–Am–F so that it begins on A minor and you get Am–F–C–G. In his 2017 analysis, Richards examines how this version can suggest either a major or a minor tonal centre. He argues that the melody plays a crucial role in shaping that perception.
His comparison of Sia’s “Cheap Thrills” and “Never Give Up” makes the point concrete. Both use the recurring sequence F♯m–D–A–E, yet Richards hears the verses leaning towards different tonal centres because their melodies emphasise different notes. Even keeping the actual chords the same can leave room for a different musical effect.
That is a more interesting discovery than simply counting how many songs share a pattern. The chord symbols leave many decisions unwritten. They cannot tell you whether the voice whispers or strains, whether the drums enter immediately, or whether the most memorable moment happens in the silence before a line.
Try a small experiment if you play an instrument. Repeat C–G–Am–F, giving every chord four beats. Hum one short tune over it. Then keep the chords exactly as they are and invent another tune with a different rhythm. Record both. Listen for which notes you linger on and where your phrases begin and end.
You may like one version much more than the other. That difference is where the work becomes interesting. Four familiar chords can get a song started; the decisions that follow give someone a reason to remember it.