If you haven’t already, watch the video above. Odd isn’t it? How can 4 chords create so many different songs? What are these magical four chords and how do they work?

Before we can answer those questions, we need to have a basic understanding of music theory. In western music there are a total of 12 notes. These notes have intervals of half steps and together form the Chromatic scale. After the twelve notes the pattern repeats:

Beginning with the chromatic scale, we can then derive other scale formulas. The two most popular being the major scale and the natural minor scale. These scales are defined by a pattern of whole steps [W] and half steps [H]. Whole steps are simply two half steps. Both of these scales consist of 7 of the 12 total notes and begins with a root note [R].

Major Scale: R, W, W, H, W, W, W, H

Natural Minor Scale: R, W, H, W, W, H, W, W

Now let’s look at these scales in practice. For example, C Major Scale and A Minor Scale:

C Major Scale: C, D, E, F, G, A, B, C

A Minor Scale: A, B, C, D, E, F, G, A

For the purpose of this exercise, I’ve purposefully chosen two scales that don’t use any sharps or flats, however, you may apply major and minor scales to any of the other notes which would incorporate sharps/flats to varying degrees. Next, let’s assign Roman numerals to each of the notes. For the key of C Major, this would look like this:

C = I – D = ii – E = iii – F = IV – G = V – A = vi – B = VII (note: the upper/lowercase)

And for the Key of A Minor:

A = i – B = II – C = III – D = iv – E = v – F = VI – G = VII (note: the upper/lowercase)

Now that we’ve selected a couple of keys and have assigned roman numerals to each of their notes, let’s figure out what those four chords are! In music theory, numbers I, IV and V have a relationship called harmony. It is these numbers (1, 4 and 5) that determine 3/4 of the four chords used in the video above.

In order to go from notes to chords, we simply apply each note to it’s corresponding key. So for the C major scale, the chords I, IV, and V would be C Major, F Major, and G Major. For the A Minor scale, the chords i, iv and v would be A Minor, D Minor, and E Minor. You should think of numbers I, IV and V like x, y and z variables in math- they change based on the key they are in.

The process of changing these variables to different keys is known as transposing. This is often done to accompany the singers voice- and is exactly what the Axis of Awesome do in the video.

Below is the key of C Major transposed to a number of other keys:

So what about the last chord? The last chord is the number VI (major) or vi (minor). Number VI is unique from the other chords in that it uses the opposite chord type. So for example in C Major, the vi (notice this is lowercase) would be an A minor chord rather than an A major chord. In contrast, in A Minor, the VI (uppercase) would be C major.

The VI distinguishes itself by giving contrast to the other three chords and ultimately helps create an emotional appeal. And that’s exactly why these chords are used so much in popular music. Something else to note is that in the video these chords are played in the same progression throughout (I – V – vi – IV). You can change the order of these chords, switch between them multiple times, or even add some new chords to the mix to create an almost endless number of possibilities.

Another important thing to note, which I don’t think many beginning songwriters realize, is that chord progressions are not protected by copyright. Melody and some other music elements are (I will discuss this more in depth in a future post).

Understanding how these four chords interact can substantially improve your songwriting abilities and how to compose with other musicians. Happy writing!