Demonstrate how to construct a 12-bar blues progression in three different keys, including appropriate chord voicings and rhythmic patterns.
The 12-bar blues is a fundamental structure in blues music, and while the basic chord progression remains consistent, its application in different keys and with varying chord voicings and rhythmic patterns creates diverse sonic landscapes. Let's examine the construction of the 12-bar blues in the keys of A, E, and C.
First, let's establish the basic 12-bar blues structure: it generally consists of three four-bar phrases following this sequence: four bars of the I chord, two bars of the IV chord followed by two bars of the I chord, and then one bar of the V chord, one bar of the IV chord, and two bars of the I chord. Often, dominant 7th chords are used.
In the key of A, the I chord is A7, the IV chord is D7, and the V chord is E7. The typical 12-bar blues progression in A would therefore be:
Bar 1-4: A7 | A7 | A7 | A7 |
Bar 5-6: D7 | D7 |
Bar 7-8: A7 | A7 |
Bar 9: E7 |
Bar 10: D7 |
Bar 11-12: A7 | A7 |
An appropriate chord voicing for A7 would be the standard open voicing (x02020), and for D7 (xx0212), and for E7 (020100), however these are just suggestions and there are many ways to voice these chords. For the rhythmic pattern, we can use a basic shuffle rhythm, which is often notated as a triplet feel. This is achieved by strumming on the offbeat of a triplet feel. This creates a swing feel, which is characteristic of blues music. An example would be to strum all downstrokes on the offbeats and add in ghost notes as well.
Now, let’s look at the same structure in the key of E. The I chord is E7, the IV chord is A7, and the V chord is B7. The progression would look like this:
Bar 1-4: E7 | E7 | E7 | E7 |
Bar 5-6: A7 | A7 |
Bar 7-8: E7 | E7 |
Bar 9: B7 |
Bar 10: A7 |
Bar 11-12: E7 | E7 |
For E7, we could use a standard open voicing (020100), for A7 (x02020), and for B7 (x21202). An alternate voicing for E7 could be a movable E7 (776757). We could use a walking bass pattern on the lower strings with rhythmic upstrokes on the higher strings. The walking bass line on the E7 would be roots, 5ths and octaves. For A7 it would be roots, 5ths and octaves, and for B7 it would be roots, 5ths, and octaves. You would alter the bass notes around the beat to make the walking pattern more compelling and swing rhythmically. This introduces a more rhythmically active approach, giving a more driving blues feel.
Finally, let's examine the 12-bar blues in the key of C. The I chord is C7, the IV chord is F7, and the V chord is G7. The progression would be:
Bar 1-4: C7 | C7 | C7 | C7 |
Bar 5-6: F7 | F7 |
Bar 7-8: C7 | C7 |
Bar 9: G7 |
Bar 10: F7 |
Bar 11-12: C7 | C7 |
For C7, an open voicing might be (x32310), for F7 (131211), and for G7 (320001). In the key of C a common rhythmic pattern would be to use a more straightforward strumming pattern that emphasizes the downbeats and with slightly varying rhythmic patterns on each chord. This helps create a more driving feel and makes the chords sound more forceful. A variation of this would be to use a triplet feel within the strumming. Another variation would be to only use downstrums on every other chord for a more laid back blues feel.
In all three examples, the use of 7th chords is essential to give that blues tonality. The chord voicings can be adjusted according to the desired sound and the interplay of other instruments. Rhythmic patterns should be altered and varied to add interest to the progression. These examples provide a foundation for constructing a 12-bar blues in three keys and illustrate the diversity of voicings and rhythms that can be applied, demonstrating the versatility of the blues progression.