An Introduction To The 12 Bar Blues

If you want to play blues guitar, you need to start by learning the 12 bar blues.

The 12 bar blues is the structure upon which blues music is built. It has been used since the inception of the genre and appears in almost every iconic blues song ever written. It provides the framework for the blues and will help you learn a wide variety of blues songs, as well as jam confidently with other musicians.

If you are new to playing the blues, then this article will outline some of the key concepts you need to get started. It will cover the structure of the blues, some theory, and how you can apply this knowledge to your playing. After reading, you will be able to play the basic form of the 12 bar blues across a variety of different keys.

Then over the next month or so, we will look at how you can develop these basic ideas. We will look at common variations on the form, how to add a bluesy feel to your playing and different ways of making your rhythm playing more interesting.

To start though, let’s look at the basic structure of the 12 bar blues and how it all fits together:

What is the 12 Bar Blues?

The 12 bar blues is the most commonly occurring chord progression in the blues. It has been used by blues musicians since the beginning of the 20th century and features in some of the most famous blues songs of all time, including ‘Sweet Home Chicago‘, ‘The Thrill Is Gone‘ and ‘Pride and Joy‘ (amongst countless others).

In technical terms, the 12 bar blues is a chord progression that lasts for 12 bars, or measures. These 12 bars repeat throughout the course of the song.

The chord progression is typically made up of 3 chords. Specifically, the 12 bar blues is based around the I, IV and V chords of any given key.

To understand what the I, IV and V chords are and their importance in blues, we need to delve into a little theory:

Keys, Scales & Chord Structures

Western music is based around ‘keys’. These keys refer to the scale that a piece of music is centred around. If as an example, someone says ‘this song is in the key of C’, they mean that the song is based around the notes of the C major scale.

Within the key of C (and all other keys in Western music), there are 7 notes. In the key of C, these notes are as follows:

C, D, E, F, G, A, B

Each of those notes has a corresponding number, which alters depending on the key that you are in.

In the key of C for example, the note of C is marked as 1. D is marked as 2, E is marked as 3, and so on. And in any key, the starting note – which is C in this case – is often referred to as the root note or tonic note.

Chords within a key are marked out in much the same way as the notes. The key difference is that chords are referred to using Roman numerals. So in the key of C major, the note of C would be marked as 1, and the chord of C would be marked as I.

If we were to switch to the key of A, the pattern of notes and chords would stay the same, but the specific notes and chords would change. So A would be note 1, and an A chord would be referred to as the I chord. The key still features the same 7 notes that appear in the key of C, but the starting point is different.

The I, IV & V Chords

Let’s apply these ideas to our 12 bar blues structure. We know that in the key of C, the notes of the scale are as follows:

C, D, E, F, G, A, B

C is the root note and is marked as 1. F is the 4th note in the scale and G is the 5th. As mentioned above, chords within a key follow the same pattern. The only difference is that they are marked with Roman numerals, rather than numbers. From here then, we can see that in the key of C – the I, IV and V chords are as follows:

C  F  G
(I)   (IV)   (V)

The amazing thing, is that you can apply this idea to any key. You just need to count up from the root note of the key. So if someone tells you that a song is in the key of A, all you need to do is map out the notes of the A major scale, and then pick out the I, IV and V chords from there. In the A major scale, the notes are as follows:

A, B, C#, D, E, F#, G#

Looking at the key of A then, we can see that the I, IV and V chords are as follows:

 A      D      E
(I)   (IV)   (V)

You can apply this formula to any key. If as an example you know that a blues song is in the key of D and it also follows the 12 bar progression, you can work out which chords will appear in the song by mapping out the notes of the scale and picking the I, IV and V chords from there.

A Note on Sharps and Flats

When you do this, make sure you look at the specific notes that appear within the key you are playing in. Don’t just take the root note and count up to the 4th and 5th scale notes from there. Doing this will eventually get you into trouble, because in most keys some of the notes in the scale are either sharp (#) or flat (b).

Take the key of B as an example. The notes of the B major scale are as follows:

B, C#, D#, E, F#, G#, A#

Here we can see that the 5th note of the scale is sharp. So in the key of B, the I, IV and V chords are as follows:

 B      E      F#
(I)   (IV)   (V)

So when playing blues in the key of B, you have to play an Ffor the V chord.

I don’t want to get too deep into the theory of what sharps and flats are and why they appear in different keys. But it is important to know that they appear in every key apart from the key of C. Luckily, many of the key signatures that are used commonly in blues are guitarist friendly, as the 4th and 5th notes of the scale are neither sharp nor flat. In other words, the IV and V chords are neither sharp nor flat, and you have nothing to worry about.

As we saw with the key of B though, this isn’t always the case.

I will cover what sharps and flats are and why they appear in certain keys in a future article. For now though, just be aware that you need to look at the specific notes within a key before you start playing a blues progression based within that key. This will ensure that you play the right chords, which is always a good thing!

The Pattern of the 12 Bar Blues

Now we know the structure of the 12 bar blues and how to apply it to different keys, we need to learn how the I, IV and V chords fit together within the progression. Luckily, this is nice and easy.

The 12 bar blues is easiest to understand if you break it down into 3 sections – each one 4 bars long.

The first 4 bars run as follows:

I, I, I, I

In the second 4 bars, there is the introduction of the IV chord, and the 4 bars run like this:

IV, IV, I, I

In the final – and most interesting section of the progression – there is the introduction of the V chord:

V, IV, I, V

This final section of the 12 bar blues is also called the ‘turn around’, because it concludes the 12 bar progression and takes you back to the start.

Written out like this, the progression just looks like a collection of random numerals. But when we put all of the pieces together, the progression (hopefully!) becomes much clearer:

This shows you how the progression is structured. The next step from here is to apply this structure to a specific key. Sticking with our example of C, the 12 bar blues in the key of C is structured as follows:

Try playing this progression in C until you become familiar with the chord changes and how the progression sounds. Once you’ve nailed that, switch keys and then play through the progression in the keys of A, B, D and E etc.

At this stage, please don’t worry about rhythm, your strumming pattern or the voicings you use for chords. If you know how to play barre chords, I would recommend playing the progression in that way, rather than using open position chords. If not, then don’t worry – I will be covering chords and how to use and apply them to the 12 bar blues progression in my next article on the topic.

The key aim here is to get to grips with the form of the blues. Once you have that sorted, we can then look at how you play the progression to make it more interesting.

The Next Steps

You may have noticed when practicing that the progression I’ve outlined above doesn’t actually sound that ‘bluesy’. The reason for this is two-fold:

As noted, we haven’t yet established a proper bluesy rhythm or strumming pattern. The form of the blues is really quite basic, and so the rhythm you use and the groove you add to your playing is hugely important. It is a whole topic in itself and one that I will cover in more detail in a future article.

Secondly, the chords outlined here are unlikely to be the ones that blues musicians would use. Typically blues musicians don’t play straight major chords, as we have done here. Instead they play what are known as Dominant 7th chords. These chords sound less ‘happy’ than straight major chords and they add a tension to the music that sounds distinctly bluesy. Again I will cover this topic in much more detail in a future article, as it is such a key part of effective blues rhythm guitar playing.

For now though, just get to grips with the form of the 12 bar blues. I cannot stress how important it is for your development as a blues guitarist. It will open up the world of blues guitar for you and will really set you up to play amazing rhythm and lead blues guitar.

Let me know how you get on, and if you have any questions – pop them in the comments below or send me an email on [email protected] 🙂




Study Bass, Musician TUTS, Guitar LessonsStudy Bass, Music Theory Fundamentals


  • This article matching with this Dominant7 [ Article Working together gets me going with basic rhythm blues… Thanks

    • Thanks so much for taking the time to comment Witee. I really appreciate it and I’m very glad to hear that you found the articles useful. If you ever have any questions about blues rhythm guitar or if there is anything else I can help with, just let me know. You can reach me on [email protected] and I’m always around and happy to help!

    • Thanks so much Ben – I really appreciate the comment and I’m very glad to hear that you found the material on Peter Green useful! 😁

    • You’re very welcome Jesse and I’m so glad to hear you found the article useful. If you ever have any questions that I can help with, please do let me know. You can reach me whenever on [email protected]! 😁

Leave a Reply

Your email address will not be published.