Twelve Bar Blues
As I mentioned before, Scales and Chords can be regarded as the ribs and spine of harmonica playing (or any form of music for that matter...). However, like any skeleton, the individual bones aren't much use unless their put together in the right order and in the right place, the same is true for the musical skeleton.
Chord Structures
Just as certain notes sound good together when they are played as Chords, certain Chords can be combined to form a 'CHORD STRUCTURE'. A Chord Structure is basically a series of Chords played in a certain order, with each Chord played for a certain period of time. That's all. Just as Scales can be considered the musical alphabet, so to can Chords be considered as words and Chord Structures as phases or sentences. Putting this all together we can see how different words can convey very different meanings (just like Major or Minor Chords create different sounds), and, when put together into sentences, can deliver complete messages designed to provoke thought or feeling.
For example, consider the phrase:
"Fair is foul, and foul is fair. Hover through the fog and filthy air."
Now, you may not know where this phrase came from, who said it, and to whom, but you can hazard a guess that it's not particularly pleasant. The words "foul" "fog" and "filthy" aren't exactly going to inspire you to wrap Christmas presents, are they? Even the word "fair" slotted in occasionally doesn't seem to improve the idea behind it. Now, if the same words were thrown together in a totally random order (let's say "Hover, and foul foul the air fog is and filthy fair through is fair.") the effect wouldn't be nearly as powerful. You might get a rough idea of what might be going on in the background, but you wouldn't be sure and it would hardly sound scary. The same is true for music, by combining all the elements together in a way that is understandable and makes sense you can tell stories, throw tantrums, or confess love by making noises on a small, tinny instrument. (By-the-way, it was the witches in Shakespeare's "Macbeth" casting a curse at the beginning of the play - very pleasant (!))
There are many different types of Chord Structure. Some styles of music, such as Blues, have just a single, main Chord Structure, whereas others like rock, pop, and jazz can have any number of different Chord Structures ranging from several to several hundred.
The Twelve Bar Blues Chord Structure
The 'TWELVE BAR BLUES STRUCTURE' is the bedrock of Blues music. It is the foundation that one builds on, the basic script that begins "Once upon a time..." and finishes with "... happily ever after." From the Chord Structure you can work out how it starts and ends, all you need to do then is jazz up the story-line a bit with a few interesting notes and Chords. Just like several hundred swear words, a couple of car chases, and the odd debate about birth control can turn an otherwise boring Tarantino script into something just about bearable.
Now, the twelve bar Blues Structure (also called the 'TWELVE BAR BLUES') is by no means the only Chord Structure used in Blues, but it is the most popular and probably the easiest to learn (thankfully!). It also appears frequently in a lot of rock, jazz and country music. If you want to play the Blues anywhere with anyone then you will need to learn the Twelve Bar Blues. No question.
Before we carry on I should clear up one or two things you may not be so familiar with: The word 'BAR' refers to a set number of beats within a piece of music, usually three or four beats of time. If you have ever seen a piece of written music you will have noticed vertical lines dividing the horizontal strips that the musical notes are written on. These lines represent the end of a previous bar and the beginning of a new Bar, and are often used as guides to split music up into smaller pieces; much in the same way that a written paragraph is divided into sentences and phrases. They help musicians keep 'RHYTHM' (the regular pacing beat to which music is played) which makes music easier and more pleasurable to listen to. This is important because - going back to the analogy with written language - if you can imagine how a speaker or an actor or a politician sounds when they give a stirring monologue (the good ones anyway!) to an audience, they often try to keep their speach patterns fluid and regular, this makes their words easier to follow and understand. Now try imagining how effective such speaches would be if the speakers decided to speed up and slow down at random; not only would they be less effective, they would sound completely ridiculous. Usually, a single Bar is divided into four beats, so a Twelve Bar Blues would be 12 X 4 beats = 48 beats. And this Twelve Bar Structure is usually repeated three or four times (each time it is played is called a 'VERSE'). You can think of Verses as being like chapters in a book; each part of the same story, but telling different bits of the tale with different characters and situations.
The Twelve Bar Blues usually uses just three Chords (what a relief!). These Chords will always have the same relationship to each other: They will be Chords formed on degrees I, IV, and V of a Major scale (they can also be refered to as the 'TONIC CHORD', 'SUBDOMINANT CHORD', and 'DOMINANT CHORD'). These three Chords can be either Major, Minor, or 7th Chords depending on the type of character you want your music to have.
The Twelve Bar Blues in G
It may seem surprising when I tell you that, when using a C harmonica, the easiest Twelve Bar Blues to play is in the Key of G. I will explain why this is later on when we discuss 'HARMONICA POSITIONS', but for the moment suffice it to say that the reason is because the three Chords needed for a Twleve Bar Blues in G (namely G,C, and D) are all conveniently located on the C harmonica.
| BLOW | C | E | G | C | E | G | C | E | G | C |
| HOLE | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| DRAW | D | G | B | D | F | A | B | D | F | A |
Looking at the layout of the C harmonica once again, you may recall from the section on Harmonica Theory that blowing into any three holes in a row will produce the C Major Chord (C-E-G), drawing on holes 1, 2 and 3 will produce the G Major Chord 2nd Inversion (D-G-B), drawing on holes 2, 3 and 4 will produce the G Major Chord Root Position (G-B-D), and drawing on holes 4, 5 and 6 will produce the D Minor Chord (D-F-A). If you delve a little deeper you will notice that drawing on holes 2, 3, 4 and 5 will produce a 'DOMINANT 7TH CHORD in G' (G-B-D-F). This is really good news because pretty much any 7th Chord is guaranteed to sound Bluesy. Remember that the Dominant 7th Chord is formed on the Dominant (V) Degree of a Major, Harmonic or Melodic Minor Scale. In the case of C Major/Minor, the Dominant note is G. If we look at the notes within each Major and Minor Scale in C, we can see how the Dominant 7th Chord in G is formed by notes G, B, D and F.
| Degree | I | II | III | IV | V | VI | VII | I |
| Major | C | D | E | F | G | A | B | C |
| Natural Minor | C | D | Eb | F | G | Ab | Bb | C |
| Harmonic Minor | C | D | Eb | F | G | Ab | B | C |
| Melodic Minor | C | D | Eb | F | G | A | B | C |
It becomes clear that all the Scales contain the notes G, B, D and F - except the Natural Minor in C which has a Flattened B - and so can form a Dominant 7th Chord. Incidently, drawing on hole 2, 3, 4, 5 and 6 together produces a 'MAJOR DOMINANT 9TH', but you don't really need to worry about that.
It seems amazing that so much versitility is contained in our small, tinny sounding instrument, but there are other Chords available that I haven't even mentioned! So there you have it: A multitude of Chords available for adding colour, style and character to our music, all perfectly located for playing the Blues.
The Chord Structure
So finally we're going to get down to the actual Chord Structure... Sorry it took so long, but I think you'll be wiser for the longer route [;-)]
| Chord | Number of Beats | Number of Bars | Degree Names |
| G | 16 | 4 | I (Tonic) |
| C | 8 | 2 | IV (Subdominant) |
| G | 8 | 2 | I (Tonic) |
| D | 4 | 1 | V (Dominant) |
| C | 4 | 1 | IV (Subdominant) |
| G | 8 (inc. Turnaround) | 2 (inc. Turnaround) | I (Tonic) (inc. Turnaround) |
If you practise with passion then very soon you'll find yourself following this Structure without even thinking about it. Listen to a few well-played Blues tunes and see if you can follow the beat and spot the places where the Chord changes occur. After a while it will seem like second nature.
Turnaround and Introduction
Many, many Twelve Bar Blues tunes end each Verse with a 'TURNAROUND'. This is basically a few beats worth (two to four usually) of the Dominant (V) Chord at the very end of a Verse to build tension and give a clear warning that the next Twelve Bar Structure is about to start. It's simple but extremely effective. Have a listen to some classic tunes and you'll probably hear Turnarounds in all of them.
Less common (but still popular) is the 'INTRODUCTION'. This is usually a short Chord Structure (usually two or four Bars long) designed to launch the musicians into the main Twelve Bar Blues part of the tune. There are two main types of Introduction: The first is two Bars long and is identical to the last two Bars of the Twelve Bar Blues (i.e. two Bars of the Tonic Chord including a Turnaround); The second is four Bars long and is identical to the last four Bars of the Twelve Bar Blues (i.e. one Bar of the Dominant Chord, one Bar of the Subdominant Chord, and two Bars of the Tonic Chord including a Turnaround). Introductions are usually less of a worry to a harmonica player because it is usually much easier to join in a tune once you have the Rhythm in your head.
Now that's all covered, let's talk about something a little more meaty - let's talk about different positions...