In this free guitar lesson, I’m going to explain why a blues chord progression is not 1-4-5, technically. If you think a blues chord progression is 1-4-5, you’re missing one of the most important aspects of the blues. Let me explain…
Blues Chord Progression
To begin, think of a typical 12-bar blues in A. You make use of the three major chords in the key of A, which are A, D, and E. These chords are 1, 4, and 5 in the scale. Instead of playing plain major chords, blues players use dominant 7th chords.
But, wait a second… while you can build plain major chords with the A scale, you can’t build all these dominant 7th chords. Let’s go through each chord and see how it relates to our key scale, A major.
Dominant 7th Blues Chords
A dominant 7, or simply A7 for short, is built 1-3-5-b7 which consists of the notes A-C#-E-G. Notes A-C#-E are in the A scale. They make up an A major chord which is chord 1 in the A scale. But the b7th, G, is not in the scale. Instead, the scale has a major 7th G#. The 1 chord, A, should be an Amaj7, not an A7.
Taking a look at the 4 chord in our blues progression, it’s D7 which is also 1-3-5-b7 or D-F#-A-C. But the A scale doesn’t have a C natural. Instead, it has a C#, so the 1 chord, D, should also be a major 7.
Finally, the 5 chord, E7, is 1-3-5-b7 or E-G#-B-D. No conflict here as all these notes are in the A scale. In fact, it’s only the 5 chord in a key that naturally produces a dominant 7th chord. The other major chords in a key are major 7ths.
Since there’s only one dominant 7th chord in a key, and since our blues progression uses three different dominant 7th chords, do you know what this means? It means this blues progression is drawing notes from three different scales. It’s actually three different keys with each chord being the 5 chord from a different major scale.
Really? Yes, really!
Right now you might be thinking, “Whatever, it’s still based on A, D, and E which are 1, 4, and 5. There’s no need to overthink it.”
If you want to truly understand how blues music is composed and how blues guitarists get creative with their lead lines, you need to unpack this stuff. Let’s do that now so you see the benefits.
If the 5th of a scale is the only degree where you can naturally build a dominant 7th chord, then from which scale is A7? A7 is the 5 chord in the D major scale. This means you should play D major scale notes over the A7 chord. When you play the notes of D major but use the 5th, A, as your starting point, it’s called Mixolydian mode. This mode, which centers on a dominant 7th chord, is also called the dominant scale.
Moving on, from which scale is D7? D7 is the 5 chord in the G major scale. This means you should play G major scale notes over the D7 chord creating the sound of D Mixolydian mode or the D dominant scale.
Finally, we already figured out that E7 is from the A major scale, so you should use A major scales notes creating the sound of E Mixolydian mode or the E dominant scale.
So, we have established that this blues progression makes use of notes and chords from three different keys. Each chord in the progression is essentially a key change. But do blues players really play this way? Absolutely! Have you ever heard or played a walking blues bass line? Bass lines (and also blues riffs and rhythm guitar patterns) draw from all three scales by making use of 1-3-5-6-b7 on each chord. Guitarists also sometimes change scales in their lead lines by playing each chord’s dominant scale.
Now, another guitar soloing option involves playing one pentatonic scale over a whole blues chord progression. In this case, you could stay in the key of A minor pentatonic while the chords change underneath. This is, by far, a much simpler option, and often how guitarists get started with playing the blues. It’s also a good-sounding option and often taking a different approach isn’t necessary.
But, if you truly want to understand everything you hear in blues music, and if you want to take your solos in a more melodic and jazzy direction, you need to take into consideration that, technically, each chord in a blues song is a key change.