By Jeffrey Pepper Rodgers

The chord trinity known as I–IV–V is one of the most useful theoretical concepts for any musician. The I–IV–V is a skeleton key for countless songs in folk, country, rock, blues, and beyond, revealing the basic similarities of, say, “Louie Louie,” “Ring of Fire,” “Johnny B. Goode,” “Helpless,” “Three Little Birds,” “I Still Haven’t Found What I’m Looking For,” “This Land Is Your Land,” “Man of Constant Sorrow,” and “I Fought the Law.” Understanding I–IV–V progressions can help you jam along with songs you’ve never played before or change a song’s key without using a capo, and it can get you started writing your own songs, too.

In this lesson, I’ll explain what I–IV–V means and how these chords lay out in various keys. Then you can play through some examples as used in classic songs.

Chords by Number

In a nutshell, the I, IV, and V are the most commonly used chords in any major key. All three chords are built from notes in the key’s corresponding major scale. Take the key of C major, for instance. Here are the notes in the C major scale, numbered 1 to 7.

C       D       E       F       G       A       B
1       2       3       4       5       6       7

The I chord is built from the first note of the scale, a C—when you stack two other notes from the scale on top (moving up the scale, you add the third and the fifth notes, E and G), you get a C major chord. The I is the tonic chord in the key—the harmonic home base—and gives the key its name. The IV chord is built similarly from the fourth note of the scale (F, with A and C then stacked on top) and is an F major; and the V chord, built from the fifth note of the scale (G, plus B and D), is a G major. An uppercase Roman numeral means the chord is major; lowercase is used for minor.

You can find the I, IV, and V chords in any other key the same way—by building from the first, fourth, and fifth notes in the corresponding major scale. Here are the I, IV, and V chords you get in the five easiest keys on the guitar.

I       IV      V
C       F       G
A       D       E
G       C       D
E       A       B
D       G       A

Since these groups of chords are all built from the same pattern in their respective keys, they fit together the same way. A song that goes, say, from C to F to G in the key of C is using the same underlying progression as a song that goes G–C–D in the key of G, or another song that goes D–G–A in the key of D. These songs are all I–IV–V.

Take Two

To get a handle on how the I, IV, and V work together, start by focusing on pairs of chords—first, the I and IV. Think of these as the “amen” chords: in a typical ending of a hymn, the IV comes with the “ah” and resolves to the I on “men.” Some songs use only the I and IV. One classic is Sly and the Family Stone’s “Everyday People,” which is the basis of the first set of examples.

Play the two-bar rhythm pattern in the key of G in Ex. 1a As you can see, the IV (C) makes only a brief appearance at the end of measure 1. Use the G fingering shown, with the ring, middle, and pinkie, to speed up the change to C and back. Take it slowly and loop the example—all examples in this lesson are designed to be looped. In Ex. 1b, play the same pattern in the key of A, where the I is A and the IV is D. (Note that I’m using a less common fingering for A that makes for a smooth change to D because the index can stay planted on the third string, but you may prefer another fingering.)

Now try this pattern in three other keys: C (Ex. 1c, where I is C and IV is F), D (Ex. 1d; I is D and IV is G), and E (Ex. 1e; I is E and IV is A). Can you hear how these are all the same progression transposed to different keys?

Basics1-4-5-1

Try singing a bit of “Everyday People” over each one of the examples (“and so on and so on and scooby dooby doo . . .”). You just need to find the right starting note for the melody in each key.

Next, check out the I and V. The V is the crucial chord that resolves most powerfully to the I. Hank Williams’ ever-popular “Jambalaya” uses only the I and V in a repeating eight-bar pattern. Try it out in Ex. 2a, in the key of C: I is C and V is G. Play an alternating bass/strum pattern with a short bass run in measure 6. Then play the same basic pattern in D (Ex. 2b) and in A (Ex. 2c). Regardless of the key, the relationship between the I and the V is the same.

Basics1-4-5-2

The Big Three

Now put the I, IV, and V together. With a nod to Richard Berry, who waited far too long to get proper credit and compensation for writing “Louie Louie,” play that song’s signature rhythm in the key of A in Ex. 3a. The progression goes I–IV–V–IV (in A, that’s A–D–E–D), climbing up and back down. Once you’ve got that rocking, try it in G (Ex. 3b, G–C–D–C) and in C (Ex. 3c, C–F–G–F).

The I, IV, and V can be reshuffled in any order in a song. The final set of examples shows a strumming pattern similar to what Neil Young uses in “Helpless,” which goes I–V–IV. In the key of D, that’s D–A–G (Ex. 4a). In G, I–V–IV is G–D–C (Ex. 4b), and in A it’s A–E–D (Ex. 4c).

How to Use the I–IV–V

Once you can quickly find the I, IV, and V in various keys, all sorts of useful things become possible.

If you’re singing a I–IV–V song in G and it’s a little low for your voice, rather than capoing up the neck you could just play the I–IV–V in A. At a jam session, when someone kicks off a bluegrass or traditional folk song, you can bet good money it’ll use the I, IV, and V—and you’ll know where to look for the next chord. Whenever you’re learning songs, you’ll see these three chords at work, by themselves or in conjunction with other chords.

And as the saying goes (usually attributed to Nashville songsmith Harlan Howard), all you need to write a song are three chords and the truth. Now you know a great place to find the three chords. Take the I, IV, and V in any key, shuffle them around, find a groove, start singing, and see what happens.

As for the truth . . . well, it’s out there.

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