I–vi–IV–V? Learn the Roman Numeral System to Play Better with Others—and Improve Your Ear


Have you ever been to a uke jam and heard the leader call out, “Key of F—four, five, one” while wondering to yourself what this secret code might be? The approach of assigning numbers to chords is called the Roman numeral system. Our goal is to use numbers to describe chords and their progressions so that we can easily identify patterns regardless of what key we’re playing in. 

In this lesson, we’ll learn how to build chords starting on each note of the major scale. Then we’ll explore some common chord progressions found in thousands of songs. You’ll see how using numbers allows you to see the patterns that occur in your favorite tunes, regardless of what key they were recorded in, so that you can eventually play them in any key.  

Building Chords and Numbering Them

Let’s start off with everyone’s favorite key signature, C major. If you’re visualizing a keyboard, C uses only the white keys of the piano and the tonic, or home base, is the note C. Thus, the C major scale has seven notes—C D E F G A B—as shown in Example 1

Now let’s explore some three-note chords known as triads, starting with C as the root (Example 2). Using only the notes in the key of C, build the chord up in thirds, first adding E, which is a major third (two whole tones) above C. Stack another third, this one minor, on top of E by adding the note G (the fifth of our chord). So our C chord has the notes C, E, and G, and it is a major triad, as determined by its third. We’ll designate this with the Roman number one (I), using an uppercase letter for major. This is our “one” chord. No matter what key we are playing in, the I is built on the tonic (the note that gives its name to the key). 

Try this for the other chords in the scale, all of which are shown in Example 3, where you’ll notice that the common ukulele voicings double one of the notes in each chord. Build a triad starting on the second degree, which, in the key of C, is the note D. Add the third above that (F), which is a minor third (a whole step plus a half) up from D. Stack another third on top of F by adding the note A, the fifth of this chord. The resulting chord, D minor, has the notes D, F, A. Owing to that first third, this is a minor triad, designated by the lowercase m. Label this as ii—our “two” chord. 


The “three” chord (iii) is built on the third degree of the scale. It’s another minor triad (Em), built on E and containing the notes E, G, and B. Form the “four” chord on the fourth degree of the scale (F A C) and you have a major triad (F), since the interval between F to A is a major third. So we’ll label the F chord with an uppercase numeral IV. Similarly, the major “five” chord, expressed as V, is built on G and made up of the notes G, B, and D.  

The “six” chord (vi), rooted on A and including the notes A, C, and E, is minor (Am). And there’s one chord that’s different from all the others. The “seven” (vii, in this case, B D F) contains two minor thirds and is therefore a diminished triad, indicated with the suffix dim. (Note that some publishers write diminished as a superscript 0.)

Endless Possibilities

You now have the ability to play thousands of songs! For example, play two beats of ii and V, followed by four beats of I, and you have the “two-five-one,” one of the most common progressions in Western music. It is the building block of innumerable jazz standards—this progression opens “Autumn Leaves”—and pop tunes. The song “Sunday Morning” by Maroon 5 is basically entirely made up of repeated ii–V–Is. Though the ii–V–I progression is typically played with seventh and other jazzy chords, it is shown in triadic form in Example 4.

Play a I–vi–IV–V progression (Example 5) and you will hear the first few bars of many pop classics—to name just a few, the Everly Brothers’ “All I Have to Do Is Dream”; the Righteous Brothers’ “Unchained Melody”; and Dolly Parton’s “I Will Always Love You,” most famously covered by Whitney Houston. 

And, as shown in Example 6, if you strum two beats each of I, vi, ii, and V, you get the famous “one-six-two-five” progression that is ubiquitous in jazz standards, from George and Ira Gershwin’s “I Got Rhythm” to Irving Berlin’s “Cheek to Cheek.”

Play It in Any Key

Of course, you don’t want to be stuck playing everything in the key of C. You want to be able to play along with your favorite records and keep up at jams. So let’s get back to that uke jam (“Key of F—four, five, one”). The Roman numeral system makes it easy to play these progressions in any key. For instance, just write out the notes of the F major scale: F G A Bb C D E. Circle the first, fourth and fifth degrees of the scale. In the key of F, the “one” chord is F, “four” is Bb, and “five” is C. Example 7 shows that I–IV–V–I progression as commonly played on the ukulele in F. 

Try practicing these progressions in other keys, too. But instead of thinking or saying the letter names of the chord, use the numbers. You’ll be amazed at how quickly you start to recognize the different progressions in your favorite tunes. You may even start to notice how songwriters use these building blocks to craft their songs, while doing wonders for your musical ear. Best of all, you won’t have to worry that musicians around you are speaking in code, because you’ve already cracked it!

Diane Nalini is an award-winning jazz singer and songwriter who teaches jazz ukulele and voice.