Chords are the foundation of Western music.
Words and melody don’t become a song until there’s harmony in the mix. That’s what makes chordal instruments like guitar or piano such powerful tools for songwriters and composers.
A chord progression is when any two or more chords are played in succession. The term often refers to common groups of chords, such as the I-IV-V progression in pop music or the ii-V-I progression in jazz.
Basic chord progressions use diatonic chords, or chords found in a single key. More advanced progressions borrow chords from neighboring or even disparate keys.
You may have noticed that every new chord you learn doesn’t necessarily work with the other chords you know.
Chord progressions are typically expressed using Roman numerals (we’ll discuss that more later). That’s because the same patterns of chords can be played in any key. Nashville musicians developed the so-called Nashville Number System to take advantage of these patterns.
Roman Numeral Analysis
Each diatonic key has seven notes. If we build a chord off each note in the C major scale, the chords will have the following traits:
That same pattern of major, minor, and diminished chords will appear in every key. Learning scales and the order of sharps and flats (see How Do You Practice Guitar With the Circle of Fifths?) will help you understand which chords fit in each key.
When we talk about chord progressions, the common way of expressing them is with something called Roman numeral analysis. This system assigns a Roman numeral to each chord in the scale. Fortunately, you can teach yourself to count to seven in Roman numerals with ease.
The numbers 1-3 are represented with one, two, or three lines (actually it’s the letter ‘I’). These can either be upper case (I, II, III) for major chords or lower case (i, ii, iii) for minor chords.
Four is a little tricky, so we’ll come back to that shortly.
The number 5 is represented by the letter V. Again upper-case (V) is a major chord, and lower-case (v) is a minor chord.
Now that you know the numerals I, II, III, and V, we can talk about the number four. Roman numerals use “subtractive notation” for the numbers four and nine. That means four is written as IV or iv. It’s a little confusing, but the simple way to understand it is “V minus I” or 5 minus one.
The same idea applies to the number nine (IX or ix), except that music theory only requires you to count up to seven.
We’re back to regular additive notation for the numbers six and seven. Six is V + I (VI or vi). Seven is V plus II (VII or vii).
Here are the numbers one through seven written out as Roman numerals:
So how do we apply these crazy Roman numerals to music?
Diatonic Chord Progressions
By default, we’re dealing with diatonic keys (major, minor, etc.). Diatonic keys have seven notes, upon which we can build a three-note chord called a triad. These seven chords follow the same pattern no matter which key you’re using.
Here is the pattern for the chords in the major diatonic scale:
You’ll notice the above example uses regular Arabic numbers instead of Roman numerals.
The Nashville Number System actually uses “regular” numerals. You might wonder why this isn’t the standard way of doing things. It requires extensive knowledge of harmony. If a chart shows a “3” in the key of C major, you have to know it’s an E minor chord. And if the singer needs you to play the song in B♭ Major, you know 3 is D minor.
Roman numerals allow musicians to talk about harmony even if everyone isn’t a music theory expert. We can see at a glance which chords are major, minor or diminished.
Here is every chord in all 12 diatonic keys:
Examples of Chord Progressions
Let’s say you memorize the chart with all seven triads in all 12 keys. What are you supposed to do with that information?
The most useful aspect of knowing your chords is that you can begin learning to identify common chord progressions in your favorite songs and in your compositions. Not only does this help you learn songs faster, it also gives you the tools for setting a musical “mood” without too much hassle.
Here are a few of the most common chord progressions you’ll find in popular music:
I – IV – V
Countless traditional folk and country songs—as well as hit pop songs—have been written with these three chords. Because it uses all three major chords in the key, it tends to sound bright and upbeat.
You’re already familiar with it if you’ve ever played a song with C, F, and G. Think “La Bamba” by Richie Valens and “Twist and Shout” by The Beatles (the original song by the Isley Brothers uses the same progression in B♭).
There are probably millions of guitar-based songs taht use G, C, and D. And countless others that use A, D, and E or even E, A, and B7.
Here are all of the I-IV-V progressions you can play with open chords:
Obviously there are more than five keys. But you probably aren’t looking for information about basic chord progressions if you can conceptualize the same progression in every key.
I – vi – IV – V
This is commonly known as the “Doo-Wop” progression because so many doo-wop hits from the 1950s and early 1960s used these chords.
Examples include “Earth Angel” by The Penguins and “Duke of Earl” by Gene Chandler. While many of these songs were performed in flat keys, open chords are a good place to start on the guitar.
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*The minor vi chords in the keys of D and A major are not open chords, but they are common barre chords an advanced beginner or intermediate may know.
ii – V – I
Anyone who has so much as read the table of contents of a jazz guitar book—or watched a beginner jazz video on YouTube—has heard of a ii-V-I progression. And if you’ve read this far, now you understand what those Roman numerals mean.
Frequently, jazz standards will use extensions on top of the basic ii-V-I. At the very least you will see things like ii7-V7-I∆7. These symbols are not essential for a beginner. The Roman numerals are the most important part.
Here are ii-V-I progressions in four open-chord keys:
*The minor ii chord in the key of A major is not an open chord, but it is a common barre chord an advanced beginner or intermediate may know.
There are too many chord progressions to name. It would be tedious and possibly overwhelming to read charts laying out every progression in every key.
So here are a few other common progressions. Using your newfound knowledge of Roman numeral analysis and the charts in this article, see if you can identify songs that use these progressions and learn to play them.
- I – vi – ii – V
- I – V – vi – IV
- I – iii – IV – V
- vi – V – IV – V
There is also my personal favorite, the I – III7 – vi – IV, which I wrote an entire article about.