The Blues Progression and the Blues Scale - Introduction
The simple blues progression consists of three dominant 7th chords, I 7, IV 7 and V 7. The measure layout is as follows: I 7 (4 bars), IV 7 (2 bars), I 7 (2 bars), V 7 (1 bar), IV 7 (1 bar) and I 7 (2 bars). So blues in the key of C would be: C 7 (4 bars), F 7 (2 bars), C 7 (2 bars), G 7 (1 bar), F 7 (1 bar) and C 7 (2 bars). Before you try to improvise on the blues progression, you should first know the structure of the chords! The C7 includes the notes C, E, G, Bb (1, 3, 5, b7), the F 7 includes the notes F, A, C, Eb (1, 3, 5, b7) and the G7 includes the notes G, B, D, F (1, 3, 5, b7).
The Blues Progression and the Blues Scale - Improvisation
You can improvise on just the chord tones and that is a good place to start. It is always good to emphasize the 3rd and 7th of the chord because those tones identify what kind of chord it is! In this case the major 3rd and flat 7th reveal the dominant 7th sound! You can also improvise on dominant 7th or Mixolydian scales. They are simply major scales with flatted 7th tones like the dominant 7th chords. Remember that the 4th scale step if very dissonant against the 3rd of the chord and wants to move to the 3rd! Otherwise, any other notes in the scale will sound okay when emphasized. So, when a C Mixolydian scale is used with a C 7, C, D, E, G, A and Bb are all notes that may be emphasized. However, F must resolve to E! I call that the “amen” of jazz!
The Blues Progression and the Blues Scale - The Blues Scale
The Blues Scale is so-called because it includes notes that are considered “blue” notes, the lowered 3rd, lowered 5th and lowered 7th of the key. A Blues scale built on C has the following notes: C, Eb, F, F#, G and Bb. When used with a C 7, the Eb gives a “bluesy” sound to the chord. That is probably because Eb would be a minor 3rd in the chord and we generally seem to hear minor sounds as being sad or bluesy! However, you don’t normally have both a major 3rd and a minor 3rd in a chord so the Eb is really D#, the raised 9th of the chord! So we hear it as an alteration of the harmony. The same is true of F# which is the raised 11th of the chord. Bb, of course, is just the lowered 7th of the chord but it is not in the normal major key signature so it takes on a bluesy character!
The Blues Progression and the Blues Scale - Blues scale of the key!
The beauty of the blues scale is that it generally fits all three chords in the blues progression. Unlike other chord progressions and their related scales or modes, you don’t use a separate scale for each chord. The blues scale built on the key center works with all three chords in the progression! However, you do have to be careful of certain notes that will sound dissonant or “wrong” on each of the chords.
The Blues Progression and the Blues Scale - Dissonant Notes!
Below you will see the blues scale in the key of C shown next to each chord with the “wrong” notes in parentheses.
C7 - C, Eb, (F), F#, G, Bb - F clashes with the 3rd, E
F7 - C, Eb, F, F#, G, (Bb) - Bb clashes with the 3rd. A
G7 - (C), Eb, F, (F#), G, Bb - C clashes with the 3rd, B and F# clashes with the 7th, F
Melodic ideas moving through the scale may pass by those dissonant notes without a problem but they shouldn’t be emphasized against the chord! The best test is to play each chord on a keyboard, holding down the sustain pedal, and play the scale over it with your instrument (if you are a pianist, play and hold the chord with your left hand and play the blues scale with your right hand). Listen for which notes sound best with each chord! If you listen carefully, your ear will tell you which notes are a problem! At first improvise using only two or three notes of the blues scale and compose ideas that you like the sound of on each chord.
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