What is the "twelve bar blues?"
The twelve bar blues is the most common blues song-form. The typical twelve bar blues is based on that important chord progression from part 1 (Guitar Styles: The Blues - part 1 (IV-V-I progression, "blues scales")), the VI-V-I. This is as much a melodic format as harmonic, although that aspect is often ignored by books claiming to teach the blues. This format grew out of the Mississippi Delta and spread throughout the United States and the world. When you're improvising with a band and the band leader says "play the blues," they're expecting this twelve-bar format.
The twelve bar blues consists of twelve measures (surprised?). Four measures of the I chord, two measures of the IV chord, two measures of the I chord, a measure of V, a measure of IV, and two final measures of I. This format is divided into three sections, each four measures long.
Line #1: I-I-I-I
Line #2: IV-IV-I-I
Line #3: V-IV-I-I
Melody
The first two measures of each line holds a two measure long melody that is part of the song. When you're playing a random twelve-bar blues with an improv group, you can develop these melodies or "motifs" as you play, if you're the lead guitarist. Make sure the band understands the motif and knows that it will repeat and, if it changes, how it will change. If you're covering a twelve-bar blues song, memorize the motifs (the melodies of the first two measures of each line), and improvise melodies over the final two measures of each line. No matter what the situation, the melody of the final two measures of each line is usually improvised. The motifs could be played by a lead guitar, vocals, a piano, a saxophone, a flute, a trumpet, a harmonica, or maybe a few other instruments...The melodies filling in the other two measures of each line can be improvised by just about any instrument in the band, maybe even the bass, or the melody could be replaced with a drum fill. Remember this general format when writing a blues song.
The melody of the blues is written the same way as you would write classical melodies (covered in my music theory lessons) but with the "blues notes" (discussed in part one) added for flavor.
The melodies of classical music were written as a contrast between "conjunct" motion and "disjunct" motion. Conjunct motion means the notes are all half steps and whole steps. Disjunct motion is when a jump more than a half step is made. Disjunct motion was typically used sparingly, for interesting dynamics, but when you find larger steps one after another (a string of disjunct motion) you are probably listening to some dissonant music. The intervals of 4 and 7 (which if omitted from the major scale leave the major pentatonic scale) used to be generally avoided, but these days our ears are more used to them. This is because of the "emancipation of dissonance," which basically means that if an experimental composer uses a note that sounds like crap to our ears, our grandchildren (who will grow up with composers doing this) won't think the note sounds like crap. Due to the emancipation of dissonance, disjunct motion is far more common. In a lot of progressive rock music, disjunct motion is extremely common and our ears think its just an interesting melody.
These days, our ears are so used to dissonance, that a lot of us can listen to a blues song using all twelve notes of the chromatic scale and not notice any dissonance. These kinds of people would listen to the opposite kind of person (someone who's ears basically barf when certain notes are used) play the blues and think that its boring. People who aren't used to dissonance might want to limit their blues solos to the major pentatonic scale (1-2-3-5-6), which many of us find boring. If a more experienced blues player with more adaptable ears plays a dissonant note such as the b2, this player knows they can "resolve" the dissonance by moving it to a close consonant tone, in this case 1. The blues notes are obviously the most common dissonances in the blues (the b3, b5, and b7), but in general lead guitar playing, its interesting to throw in dissonant notes ("chromatic playing") and resolve them. The b5 is sometimes considered THE blues note, as in the note that really tells people "I'm listening to the blues."
The two methods of melody
I want to make sure you understand that these two methods are for improvisation only. When you write your motifs, hopefully you will know just by ear that it sounds good, or maybe use a combination of both of these methods. When improvising melodies, or solos, these are two important tools:
Intervals based on the key
When using this method, the 1 is the key center, always. The melody sort of "forgets" the chord progression, and doesn't think "if I'm playing the 1, during the IV chord, it is also the IV's 5." That is the other method. The method of basing intervals on the key center means you will probably create smooth melodies that tell a great story. That's a very important part to soloing: telling a great story. A good technique to playing the blues is to use this method when playing a solo, and the other method when playing the other parts of the songs.
Intervals based on each chord
This method can create some interesting melodies, but typically each melody is independent from the next, meaning it doesn't sound like a smooth solo. A good way to practice this idea if you've never tried it is to play different scales based on the each chord. For example, if you're playing the twelve bar blues in Cmajor (I is Cmajor, IV is Fmajor, V is Gmajor), you can use the Cmajor pentatonic scale over the Cmajor chord, the Fmajor pentatonic scale over the Fmajor chord, and the Gmajor pentatonic scale over the Gmajor chord. You can also "superimpose" scales and arpeggios. Experiment with the possibilities. This means you could play the Gmajor pentatonic scale over the Cmajor chord, or maybe even play the notes of a Dminor chord (a Dminor arpeggio) over the Fmajor chord...There are endless ideas here!
Call and response
I'm sure you've heard a call and response before. Maybe you've heard Led Zeppelin extending a song with a little battle between vocals and guitar. Maybe you've heard two death metal guitarists perform a dual-solo. Maybe you've heard Jimi Hendrix call and response by himself! A call and response is when a melody is played (for example, the motif in the first two measures of each line of the twelve bar blues) as a "call" and another melody "responds" to it. This can be especially interesting when played between two people, a guitar can "call" for the piano to "respond" or a vocalist can "call" for a saxaphone to "respond"...More endless possibilities! But you can of course call and receive yourself, one instrument can pull this off pretty well.
Typically, if a melody ends on a "chord tone" (a note that is in the chord being played), it sounds "resolved," but if it doesn't, it sounds like a "call" and a different instrument should play a "response." Let's use the twelve bar blues in G as an example:
Line #1: G-G-G-G
Line #2: C-C-G-G
Line #3: D-C-G-G
Let's say the vocalist sings a the motif on line #2 and it ends at the end of measure 2, where the C is about to change to a G, and the last note sung is an A. A is not a chord tone of C (C-E-G) or G ( G-B-D). The "response" should end on a chord tone of G, or maybe lead into the motif of line 3 (the motif which is played over the chords D and C).
That's all for today folks.
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