Most blues-based music uses chord progressions that rely heavily on tension and release as way to create a powerful forward motion. These points of tension and release are so familiar to our ears that our listeners would be very surprised if we stopped playing at any one of them. It's as though we set them up for a joke and then never gave them the punch line. Play through a 12-bar blues in A and then in the second chorus stop playing in the 4th bar and you’ll see what I’m talking about. Our ears hear A7 being pulled to the next chord and we’re left hanging until we hear the D7 chord. Great players exploit these points in the progression by creating solos that outline these moments of tension and release. In the following lesson I’m going to show you a few ways you can begin to build lines that really grab the listener and pull them through the tune.
Guitarists and piano players often use a dominant 7b9 chord in bar 4 of the blues (in our case A7b9) to increase tension, creating a stronger release when we arrive at the D7 chord in bar 5. Try playing A7b9 instead of A7 in bar 4 to get the sound of this chord in your ears.
Now that you are familiar with the sound of A7b9, let's take a closer look at this chord. If we remove the root of A7b9, we are left with the notes C#, E, G, Bb(A#), which spells another familiar chord, A#dim7. The notes in an A#dim7 chord are A#, C#, E, and G. If we move this chord from its place at the 6th fret to the 9th fret we get C#dim7 with the notes C#, E, G, and Bb(A#). Move this chord to the 12th fret and we get Edim7 with the notes E, G, Bb(A#), and Db(C#). Move it again to the 15th fret and we get Gdim7 with the notes G, Bb(A#), Db(C#), and Fb(E). Get the picture? The same four notes can be seen as A#dim7, C#dim7, Edim7, or Gdim7, so we can treat them as different names for the same chord. We could even choose to view these chords as dominant 7b9 chords (without their respective root) and call them A7b9, C7b9, Eb7b9, and Gb7b9 while keeping the same four notes on top.
If we use an A7b9 instead of A7 in bar4, then it stands to reason that we could also use C7b9, Eb7b9, and Gb7b9 in bar 4 as well and each would create the same kind of tension and release moving to the D7 in bar 5. Over the years, many great players have constructed solos based on this very principal. They used the notes of C7, Eb7, and Gb7 to color the A7 chord because it increases the tension in bar 4 and creates a stronger resolution to D7. (This has become a common practice not only in a 12-bar blues progression, but in other instances where A7 is followed by some kind of D chord as well.) Keep in mind…. This type of substitution only works at the point where the expected forward motion of a chord progression makes it virtually impossible to stop playing the progression at that moment. I have written out some lines to be played over the A7 chord in bar 4 of the 12-bar blues that include C, Eb, and Gb triads. These sounds might be new to your ears, so it’s important to give them time. Memorize them so you can play them with rhythmic conviction. Playing them “in time” will help you hear the tension and release. When this happens, you’re ready to create your own lines using the same approach as the greats! Good Luck.
