Understanding the I-V-vi-IV pop progression

Four chords on a loop

I-V-vi-IV is a progression common in many genres. It is also called the "Axis progression", after The Axis of Awesome, an Australian comedy group: in 2008, their medley Four Chords showed, for laughs, how many hits rest on these four chords. You can already find it in hits from the 1950s, such as the Teddy Bears' To Know Him Is to Love Him, written by Phil Spector.

In C major, the four chords are C, G, A minor and F, which the map writes C, G, Am and F. The Roman numeral under each one tells you which note of the scale it is built on; capitals mark major chords, lower case minor ones. Hence the small vi under Am, built on A, the sixth note: it is the only minor chord in the loop.

Nothing in this loop concludes: after F, C comes back and it all starts again. Many songs pick it up at another point, vi-IV-I-V (Am, F, C, G): it is the same loop, started elsewhere.

One chart, two melodies

The lesson goes round the loop four times, one four-bar phrase per round, before a final chord.

• A (bars 1 to 4), the verse: the melody circles around G, in the middle of the keyboard, and stops on it, like an unfinished sentence.
• A (bars 5 to 8): the same verse; only its last bar changes, to settle on F.
• A' (bars 9 to 12), the chorus: it leaps from G to high C and climbs to E, over the same chords.
• A' (bars 13 to 16): the chorus again, coming back down to G at the end.
• Coda (bar 17): a last, held C; the loop finally stops.

Why not A A B B, for a verse and a chorus? Because I compare the chart and the melody separately: a new letter would mean that both change. Here, all four phrases have the same chords, so they keep the letter A; the prime (A') signals that the melody has changed. The two verses differ only in their last bar: I read both as A, just as both choruses are A'. Finally, the "Phrase ending" column shows only a dash: each phrase stops on F, which does not conclude.

A broken-chord left hand

The left hand does not play the chords as blocks: it breaks them up, one note per beat, always in the same order. The root at the bottom, the tenth (the chord's third, an octave higher), the fifth, then the tenth again:

• C: low C, E, G, E;
• G: G, B, D, B;
• Am: A, C, E, C;
• F: F, A, C, A.

A tenth sounds fuller than a close third and gives the chord its character: major on C, G and F, minor on Am. Only in bar 17 do both hands play the final chord as a block: C and G in the left hand, E, G and the melody's high C in the right.

How to approach it

My plan takes you through it in 6 days. I do not point out any tricky passage: the difficulty is the same throughout. What matters is keeping the loop going without thinking, so the right hand is free to sing.

1. Learn the loop by heart, without playing. Count four beats per chord, naming them: C, G, Am, F. Then start from Am: Am, F, C, G.
2. The left hand alone: fifth finger on the bass, thumb on the tenth. If the stretch is wide for your hand, let your wrist rotate from one note to the next rather than spreading your fingers.
3. The verse, right hand alone. Sing it, then play it, noticing its two endings: on G the first time, on F the second.
4. The chorus, higher up: before bar 9, move your right hand towards high C.
5. Hands together, slowly. The right hand's eighth notes go twice as fast as the left hand's quarter notes: count "one-and-two-and", then work up towards 88 beats per minute.
6. Then make up your own. Keep the left hand going, and sing your own melody with the C major scale, starting each bar on a note of the chord.