Ever noticed how BB King’s “The Thrill is Gone” and “Rock Me, Baby” have a similar mood and feel? That’s because those songs are grounded upon the same basic chord progression. Chord progressions form the backbone of most tunes, and if you’re planning to write your own music, it’s where you should begin.

After reading this article, you’ll be able to:

  • Understand what a chord progression is, and the relationship with its key and scale
  • Learn the basics behind reading and creating chord progressions
  • Play one of the most popular blues progressions ever
  • Rock out with power chords

Major thirds and perfect fifths

Intervals denote the spaces in-between notes (whole and half steps), but the term is also used to reference a note’s ‘position’ in a scale. Here, we’ll introduce two very important ones: the major third and the perfect fifth.

As their names suggest, the major third and perfect fifth denote the notes in the third and fifth positions of a major scale, respectively. In Figure 1 below, the notes of the C major scale are laid out as they would on a fretboard. In Figure 2, the notes are labeled by their positions in the scale. The C note, being the root, is the first note of the scale, while D, E, and F are the second, third, and fourth notes, respectively.

Which means in the C major scale, the major third note is an E while the perfect fifth is a G:

Besides the root, major third and perfect fifth, there are others that we’ll cover in later lessons. They are: the major second, perfect fourth, major sixth and major seventh.

Intervals in a minor scale are similarly termed. Only the major third, major sixth and major seventh are affected—they’re now a minor third, flat sixth and flat seventh. The major second, perfect fourth and perfect fifth, however, remain unaffected. And this is simply due to the pattern of a minor scale.

Chord progressions

So what do intervals have to do with chord progressions? Well, the TL;DR answer is that it’s all in the numbers. But let’s take a step back first.

A chord progression is a succession of musical chords, which are three or more notes sounded simultaneously. (The exception to this rule are power chords, which only have two, but we’ll get to that soon.) Chord progressions form the foundation for harmony and establish a tonality or the ‘general mood’ of a song.

These progressions are typically indicated by a series of Roman numerals, which themselves point to the notes of a major scale. For instance, the “III” and “V” chords in the key of C major refer to chords whose root notes are the scale’s major third and perfect fifth, respectively: an E and a G major chord. And if those Roman numerals are lowercased—“iii” and “iv”—then you’ll want to play an E minor and G minor.

Which means if you see a “I-V” progression, you’re meant to play a major chord based on the root note of the key, followed by a major chord based on the perfect fifth of the key. In the key of C major, this would be a C major and a G major.

Let’s take a look at an example: a I-V progression in the key of G. By looking at Figures 5 and 6, you should be able to tell that a I-V progression consists of two chords, built upon the root note and the perfect fifth, respectively. In other words, this I-V indicates that the progression starts with a G major chord followed by a D major chord.

The famous I-IV-V

Listen to Jimi Hendrix’s “Red House,” and you’ll notice something interesting beneath the screaming solos and hoarse vocals: the I-IV-V progression. That’s what gives the blues its trademark sound.

How does this progression look like on the guitar? Here’s a fretboard with all the notes of the C major scale, but with the letters swapped out for their positions within the scale:

To play the I-IV-V in the key of C, you simply need to hit three chords: The first is rooted in the C (root note), the second is rooted in the F (perfect fourth), and the third is rooted in the G (perfect fifth). There are hundreds of chords you can use, each lending a different mood, but to better illustrate the principle, we’ll stick to power chords.

Power chords

A power chord is the simplest and most common type of chord used in rock, metal, indie and other guitar-led genres. It is neither a major, minor nor diminished chord, and can ‘fit’ into in pretty much any key or chord progression.

And you’d recognize a power chord’s two constituent notes—the root and the perfect fifth—from almost any medieval movie. Think of a pitched battle, with armies waiting on both sides. A horn bellows out the rallying cry: De-DUUM! That’s what a root note and its perfect fifth sound like when rung in quick succession, and that’s what makes a power chord so, well, powerful.

A C power chord, for instance, is made up of the C and G notes, while a G power chord is made up of a G and D. In the diagram below, several C, G and D notes of the fretboard are highlighted:

If all you gotta do to play a C power chord is strum a C and G note simultaneously, how many ways are there to play the chord in this diagram? There are at least three, but the most common would be to play the C note on the A string and G note on the D string. For a bigger and fuller sound, add the C (it’s a higher octave) on the G string.

Once you’ve understood how power chords work, you can apply it to the I-IV-V progression. So in, say, the key of C major, you’re looking at creating power chords from the root notes of C, F and G, in that order.

A helpful shortcut

The diagram below displays all the notes of the C major scale, but with the letters of its notes swapped out for numbers. The root, perfect fourth and perfect fifth notes have been highlighted, while the remaining notes have been darkened out.

In this diagram that depicts all the notes of the C major scale, notice the ‘L-shaped’ positions of the “4”s and “5”s, relative to the root:

Fourths and fifths can be easily identified because of their close proximity to the root. You can always find the fourth note on the next thinner string, and the fifth coming two frets up. On the next thicker string, however, you’ll see that the fifth falls on the same fret as the root, and the fourth two frets down.

All that’s left is to form power chords based on the “1,” “4” and “5” root notes. Practice this progression across strings and with different strumming patterns—and you’re on your way to laying down the groundwork for those stank-face solos.