Chord progression
I–IV–V chord progression
Three major chords, and the foundation of folk, country, early rock and roll and gospel. The first progression most players learn.
I–IV–V in all 12 keys
Every row is the same progression moved to another key. Tap a chord for its shapes, or play a row to hear it.
Why I–IV–V works
The I, IV and V chords together contain every note of the major scale, so any melody in the key fits over them. I is home, IV moves away, V creates the pull back to I. It is the shortest complete musical sentence there is.
In C, G, D, A and E the three chords are open shapes on guitar, and on piano the IV and V sit right next to each other, so changes are quick. Many tunes simply go I–IV–I–V–I, with a bar on each chord.
How to practise it
Begin with four beats per chord in G or C, then try the order I–IV–V–IV and I–V–IV–I. Sing the root of each chord as you change; it trains your ear to hear where the harmony goes.
Use the metronome: start around 70–80 BPM with two or four beats per chord, and change chords exactly on the first beat. When the changes are clean, raise the tempo in small steps and try the same pattern in two or three other keys from the table.
Choosing a key
Which key to use? Whatever suits the singer or the instrument. Guitarists usually prefer G, D, A, E and C for I–IV–V, because the chords are open shapes there; pianists often start in C. The table above has every key, and each chord links to its diagrams, so you can switch keys without working anything out.
Variations
Make the V a V7 for a stronger pull home, or end with IV–I (a "plagal" ending) for a gentle close. Stretch it to twelve bars and you have the blues.