What is a 12 bar blues?

The 12 bar blues is a chord sequence measuring 12 bars, commonly used in blues songs, but it also is used by songs that are not considered blues. This chord sequence has some variations which we will discuss in this article.

Introduction

12 bar blues guitarist

An outsider may consider that a 12 bar blues is a set chord sequence, however, as we will see there can be quite some variation. If you are going to play blues songs with others it is helpful to be aware of these variations. We are going to break down the 12 measures and discuss what are the most common changes that are played.

We are going to stick to a standard 12 bar dominant blues progression and minor blues, jazz blues or other variations (Stormy Monday blues for instance) will be discussed in other articles.

What are the basic concepts I need to know?

Before we start we need to clarify some terms.

For the basic dominant 12 bar blues, three chords are necessary. They are known as the one chords, the four chord and the five chord and can be written using roman numerals as I, IV and V respectively. The following chart shows you the actual chords played for the I, IV and V according to the key of the song:

chart of the keys and the I, IV and V chords:
Key I Chord IV Chord V Chord
E E A B
G G C D
A A D E
B B E F#
C C F G
D D G A

As mentioned previous each of these chords is a dominant chord, so each chord may be played as a major triad, a dominant 7th, dominant 9th, dominant 13th or another variation. Which exact form of the I, IV and V chords are used is a function of the of the song and the interpretation of the musicians.

For the purpose of this article we will use the basic I, IV and V notation for the 3 chords.

So let’s split up the 12 measures into 4 parts and look at the common variations:

The start of the blues, bars 1-4

There are 2 common variations here, and one slightly less common one:

Variation 1 - no quick change

Bar 1 Bar 2 Bar 3 Bar 4
I Chord I Chord I Chord I Chord

As you see this is very straight forward, the I chord is played for 4 bars. This is most common in medium fast to fast songs, on the slower songs the next variation may be used. On a slow song it is preferred to introduce additional chord changes to maintain interest. This is not a set rule, but just a guideline.

Variation 2 - quick change

Bar 1 Bar 2 Bar 3 Bar 4
I Chord IV Chord I Chord I Chord

In this case, the second bar switches up to the 4 chord. It is called a quick change. A slow blues almost always has a quick change in it. If you’re at a blues jam, it is important for the players to know whether there is a quick change or not, or else chaos can ensue and the vocalist gets annoyed quickly!

Variation 3 - starting on the IV

Bar 1 Bar 2 Bar 3 Bar 4
IV Chord IV Chord I Chord I Chord

This variation is less common than the first 2, but it is important to know. Many blues songs from the 50’s use this.

The middle of the blues, bars 5-8

Bar 5 Bar 6 Bar 7 Bar 8
IV Chord IV Chord I Chord I Chord

You can relax here, bars 5-8 are pretty much standard in a 12 bar blues, ignoring the Jazz blues of course.

The first turnaround, bars 9 and 10

A turnaround is nothing more than a way to leave the I chord and go back to it. The first turnaround leaves the I chord in bar 8 and returns to it in bar 11. Here are some interesting variations:

Bar 9 Bar 10
V Chord IV Chord

This is the standard which is the normal variation, as long as nobody says differently this will be used in a jam scenario.

Bar 9 Bar 10
V Chord V Chord

This variation is often used in faster tunes, and rock’n’roll tunes such as Johnny B. Goode.

12 bar blues band

The second turnaround, bars 11 and 12

So now we wrap up the 12 bar blues, with 3 variations, let start with the most basic one:

Bar 11 Bar 12
I Chord I Chord

Also known as “no turnaround”

Bar 11 Bar 12
I Chord V Chord

In medium tempo tunes this is the most common variation. There are plenty of turnaround phrases that can be played over these last 2 bars.

Bar 11 Bar 12
I Chord/IV Chord I Chord/V Chord

In a slow blues, this is very often played as the turnaround in bars 11 and 12. Each chord is played for half a bar.

Conclusion

We have looked into the basic variations of a major/dominant blues. This should cover about 70% of all songs you will come across in a blues jam.

Minor blues is another topic covered in another article. Of course there is also 8 bar blues and 16 bar blues to cover. Jazz blues is another thing entirely, you will be unlikely to encounter that in a blues jam.

Finally, as next steps there are a couple of things that are important for you to master:

  1. Know the basic chords (I, IV, V) in different keys. Start off with E, G, A, B, C and D.
  2. Learn rhythm patterns to play with these chords.
  3. Develop a feel for when the changes will happen. When you first start playing along to 12 bar blues you will be counting the bars as they pass. If you play along a lot then you with develop a feel for exactly where you are in a 12 bar blues, and not be counting anymore. This will give you much more freedom to focus on other things.
  4. Learn to hear these changes. Listen to classic blues songs from the 50’s. They are mostly I, IV and V chords using the variations mentioned here. Find the key of the song and try and work out which variation is being used. At first it may be hard, but you will improve with time.