Adapted from The Complete Singer-Songwriter
Chord progressions are the engine of songwriting. The melodic or lyrical hook may be what lodges in people’s heads, and an insistent beat may dominate the mix, but the chord progression is what makes everything move.
By itself, a chord is just a static thing—a few notes stacked together—but a group of chords arranged artfully in a progression creates a little harmonic journey. There’s a kind of magic in a great chord progression, a mix of soothing familiarity and thrilling surprise that has emotional power even without the melody and lyrics.
So every songwriter needs to be fluent with chord progressions, but the process of figuring out which chords to use and how to sequence them can be mystifying. You can create progressions by randomly trying chords, but with a basic theoretical understanding of chords and keys, you can zero in much more quickly on good options to try in a progression—and become a more productive and versatile songwriter overall.
Chords by number
The secret to understanding chord progressions is identifying chords in a progression by number—not by the letter names of the chords. This is the idea at work at a jam session when someone kicking off a song says, “It’s I–IV–V in G,” rather than, “The chords are G, C, and D.” What these numbers do is describe the function of the chords no matter what key you’re in; a I–IV–V in D works the same as a I–IV–V in G.
When you’re thinking of chords by number, you can quickly change a song’s key, pinpoint what’s happening in a cool chord sequence, or make connections between songs. You understand the musical logic, which in turn allows you to put that logic to work in your own songwriting.
This numbering system is based on the seven notes in the major scale, also called scale degrees. Using notes from the scale, we can build a chord on on top of each scale degree and arrive at the diatonic chords—a family of chords that occur naturally in any key. Even if you’re not familiar with any of this theory, your ears recognize how diatonic chords fit together, because you’ve heard them at work in songs your whole life.
For a full explanation of the number system, see The Complete Singer-Songwriter. For our purposes here, let's cut to the chase and say that in a major key, the diatonic chords are as follows:
I ii iii IV V vi viiº
The Roman numerals indicate the scale degree the chord is built on, as well as the type of chord: major chords are uppercase, and minor and diminished chords are lowercase (diminished chords are indicated with ° or dim). The I is the tonic or root chord and also the name of the key. No matter what key we’re in, the I, IV, and V chords are major; the ii, iii, and vi are minor; and the vii° is diminished.
So in the key of G major, for instance, the diatonic chords are:
G (I) Am (ii) Bm (iii) C (IV) D (V) Em (vi) F#dim (viiº)
In practice, what this means is that a straightforward song in the key of G might use only this set of chords. In fact, many popular songs include only three or four of the diatonic chords. Out of the universe of chords, songwriters are often working with just a handful of options.
Let’s use the number system to run through a few diatonic chord progressions in major keys, starting with the most basic. (Note to guitarists: a guitar-specific presentation of some of this material, with tab and video, is available in the Acoustic Guitar Guide titled Songwriting Basics for Guitarists.)
Just the I
Some songs don’t change chords at all—they simply hang out on the I (often, a bluesy I7 chord) and rely on the melody and groove to maintain musical interest. Check out the playlist for a few famous examples. Even though these songs don’t change chords, the accompaniment still moves—often with a bass line or riff.
I and V
If a song adds just one more chord to the I, chances are it’s the V. The move from V to I is fundamental—once the home-base I chord is established and a song goes to the V, our ears want it to resolve to the I. Rocking between I and V is more than enough tension and release on which to build a song, as proven by these classic examples.
I, IV, V
Add the IV chord to the I and V, and you’ve got the chord trinity behind countless songs. When people say all you need are three chords and the truth, these are the chords they mean. The I, IV, and V can appear in any order, as you can see in these examples.
“La Bamba,” Richie Valens:
I IV V
“Helpless,” Neil Young:
I V IV
“This Land Is Your Land,” Woody Guthrie:
IV I V I
Venturing outside the I, IV, and V, the next diatonic chord you’re likely to encounter is the vi. Many songs move between the I and vi—a smooth change because the chords have two of their three notes in common, as you can hear in “Shout.”
“Shout,” Isley Brothers
I vi / bridge I IV
One of the templates of early rock ’n’ roll is I–vi–IV–V, used most famously in “Stand By Me.”
“Stand By Me,” Ben E. King (with Jerry Lieber and Mike Stoller):
I vi IV V
The same sequence is heard in the Beatles’ “Octopus’s Garden” and the Police’s “Every Breath You Take” (in which the chords are dressed up with ninths for a jazzier sound). Reorder these four chords and you get the progressions for tons of other songs. Note that the following are examples, not complete chord charts—these songs have additional sections.
“Octopus’s Garden,” the Beatles:
chorus I vi IV V
“Every Breath You Take,” the Police:
I vi IV V vi / I vi IV V I
“With or Without You,” U2
“The Story,” Brandi Carlile:
I V vi IV
“Take Me Home, Country Roads,” John Denver:
chorus I V vi IV / I V IV I
“Let It Be,” the Beatles:
verse I V vi IV / I V IV I
By shuffling the I, IV, V, and vi around, changing how long you hold each chord, and trying different rhythmic feels, you can cover a tremendous amount of songwriting territory.
The ii and iii
By adding the ii and iii chords to your songwriting palette, you can create seemingly infinite progressions. Here are some examples, including several drawn from the songbook of Bob Dylan. Notice how “I Shall Be Released” ascends the diatonic chords like a ladder: I–ii–iii to a quick IV–V. “Like a Rolling Stone” uses a similar pattern: the verses start with I–ii–iii–IV–V, hang for a couple lines on IV–V, and then go right back down, IV–iii–ii–I.
“Friend of the Devil,” the Grateful Dead:
verse I IV I IV
chorus V ii V ii V
“You Ain’t Goin’ Nowhere,” Bob Dylan:
I ii IV I
“I Shall Be Released,” Bob Dylan:
I ii iii IV V
“Like a Rolling Stone,” Bob Dylan:
verse I ii iii IV V 2x / IV V IV V
IV iii ii I 2x / ii IV V
In these examples you can see some common functions of the ii and iii:
ii leads to V or IV
iii leads to IV
With a good handle on the I, ii, iii, IV, V, and vi, you are ready to roll for writing in major keys—and you’re also primed for our next topic, chord progressions in minor keys.
For more on understanding chord progressions, see The Complete Singer-Songwriter.