I — IV — V — vi.
That’s it.
These four Roman numerals represent 75 percent of the music we listen to today. Learn how to apply them and you can almost instantly play thousands of songs.
And it’s simpler than you think.
The Way-Too-Short Explanation of Western Music
Western music is based on a 12-note scale. If you ever took piano lessons or played in a junior-high band, you might remember that each note is assigned a letter between A and G and sometimes includes symbols like # or b. Furthermore, each note is one half-step from the next.
The full 12-note scale is called a chromatic scale, but a majority of the music we listen to actually narrows it down to just seven of those notes: the major scale. If we started at the note “G,” for example, we can write out the major scale as:
G — A — B — C — D — E — F#
These are the notes of the G major scale, but they also represent the chords that can be played in the key of G major. It’s simply a matter of remembering that the first, fourth, and fifth chords in the progression are major chords; the second, third, and sixth are minor chords; and the seventh is a diminished chord (which we can safely ignore almost all of the time!). This gives us the following chords:
G — Am — Bm — C — D — Em — F#dim
So now we can talk about Roman numerals. To make it easier for musicians to play songs in different keys, sometimes Roman numerals are used. All they do is indicate the relationships between chords in a song. You simply start at I and work your way up chord by chord to VII. And to indicate a minor (as opposed to major) chord, just use lowercase numerals.
In our example key of G major, then, you can write out all of the chords like so:
I — ii — iii — IV — V — vi — vii°
So let’s go back to the beginning of the article: I — IV — V — vi. We can now determine that this sequence refers to the first, fourth, fifth, and sixth chords of a key, with the sixth chord being a minor. So if you stick with our example key, G major, I — IV — V — vi lines up with G — C — D — Em.
And it just so happens that much of rock and pop music is based on using these four chords — and only these four chords.
How to Use I — IV — V — vi to Make Music
That means learning just four chords on a guitar — G, C, D, and Em — opens up a vast library of tunes you can quickly and easily learn to play. And if you want to learn a song in a different key, then all you have to do is repeat the exercise. So if you wanted to play songs in C major, then I — IV — V — vi becomes C — F — G — Am. Or for the key of E major, it’s E — A — B — C#m. And this approach works for any major key.
The list of songs you can play using some combination of I, IV, V, and vi chords is long and varied. And the great thing is, these chords work together in any progression, meaning you can play them in any order and they still sound good together.
For example, here are just a few examples of songs that use some or all of these chords in varying orders:
- “Johnny B. Goode” by Chuck Berry: I — IV — V
- “Sweet Home Chicago” by Robert Johnson: I — IV — V
- “With or Without You” by U2: I — V — vi — IV
- “Demons” by Imagine Dragons: I — V — vi — IV
- “Take Me Home, Country Roads” by John Denver: I — V — vi — IV
- “Save Tonight” by Eagle Eye Cherry: vi — IV — I — V
- “Glycerine” by Bush: I — V — vi — IV
Even though these songs are not all in the same key, they have the same basic chord progressions, and using the Roman numeral system makes them easy to learn and transpose to any key you want quickly.
How Music Theory Helps You Become Better at Guitar
Even learning a little bit of music theory — like I — IV — V — vi chords — can unlock all kinds of musical possibilities. If you’ve never seen this before, I’d encourage you to play around with these chords and see what songs you can figure out by ear. You might be surprised at just how many you’ll be able to play with very little effort.
And if you still doubt me, then allow me to remind you of one of the earliest viral YouTube videos that proves the point:
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