As the title of this blog suggests, the 12 Bar Blues format is the foundation of most blues music. Many people don’t know that the 12 Bar Blues format is also critical to rock and pop music. Learning the 12 Bar Blues opens up musical options and teaches the most important chord progression for guitar players.
This blog will explain the basics, including:
- Chord Structure
- Chords for Each Key
- Shortcut for Finding Chords
- Chord Progressions
- Example of a 12 Bar Blues in E
12 Bar Blues Chord Structure
The 12 Bar Blues has a very distinctive structure that can be applied to any key. It consists of arranging 3 chords in various patterns over 12 bars of music. Knowing which chords to play and when is the essence of becoming a fluent blues and rock guitarist.
Let’s start with learning which chords to play in a 12 Bar Blues song. The chords are always the (I) chord, (IV) chord and (V) chord. For clarity, these notations use roman numerals and known as “the one chord”, “the four chord” and “the five chord”. “What do the (I), (IV) and (V) chords mean?” and “Why are roman numerals used?” are very good questions. And I’m happy to explain!
To get just a bit technical into some music theory, the roman numerals denote scale degrees. And when representing a chord, they denote the root note on which the chord is built. The concept of the (I) chord, (IV) chord and (V) chord is based on the major scales. For any key, a chord built from the first note of the major scale is the (I) chord. Similarly, chords built from the fourth note of the major scale is called the (IV) chord. And yes, you guessed it, chords built from the fifth note of the major scale is called the (V) chord.
Let’s use an example to make this concept more clear and easy to understand. If we want to play in the key of A, we first start with knowing the notes of the A Major Scale.
Notes of the A Major Scale
| A Major Scale | A | B | C# | D | E | F# | G# |
| Roman Numeral | I | II | III | IV | V | VI | VII |
Aligning each note of the scale with ascending roman numerals, you will see that the (I), (IV) and (V) chords are A, D and E.
If you need a refresher on identifying the notes of a major scale, check out my blog on scales.
12 Bar Blues Chords for Each Key
Now you might be thinking, “That’s great for the key of A, but what about the rest of the keys?”
The table shown below defines the (I), (IV) and (V) chords for all keys. Notice that the note name of the key always matches the note name of the (I) chord.
| Key | A | Bb | B | C | C# | D | Eb | E | F | F# | G | Ab |
| I Chord | A | Bb | B | C | C# | D | Eb | E | F | F# | G | Ab |
| IV Chord | D | Eb | E | F | F# | G | Ab | A | Bb | B | C | Db |
| V Chord | E | F | F# | G | G# | A | Bb | B | C | C# | D | Eb |
If you’re playing other forms of chords, such as minor chords or dominant 7th chords, the notes in the table above hold true. For example, when using 7th chords the (I), (IV) and (V) chords in the key of A would be A7, D7 and E7, respectively.
Shortcut for Finding Chords
If it takes you a while to memorize the table above, don’t fret (guitar pun!). There’s an easy way to quickly find the root notes of the (I), (IV) and (V) chords within a key when the root note is on the sixth string. Let’s first review the shape of a Major Scale on the guitar fretboard.
Notice that I’ve numbered the first five notes of the Major Scale pattern. Starting with the sixth string, whichever note you’re playing is the root note, and therefore the name of the (I) chord and the key. To find the (IV) chord, just move your fretting finger to the same fret but now on the fifth string instead of the sixth string. And to find the (V) chord, just slide your fretting hand up two frets along the fifth string on the fretboard. This handy trick works for any key!
Below is an example using the key of A, with the (IV) and (V) chords being D and E, respectively.
Sometimes, you’ll find yourself wanting to play a 12 Bar Blues with the root note of the (I) chord on the fifth string instead of the sixth string. Fortunately, there’s another simple pattern to help you always find the (IV) and (V) chords. From wherever you start on the fifth string root note, the (V) chord is always the same fret just moved to the sixth string and the (IV) chord is just down two frets on the fretboard (as it always is).
Below is an example using the key of D, with the (IV) and (V) chords being G and A, respectively.
12 Bar Blues Chord Progressions
Now we’re ready to move on to knowing when to play each chord throughout the 12 bars of the song. There are three common 12 Bar Blues formats, and each of them only differs in one of the 12 bars. The three types are basic, repeating and quick-change.
12 Bar Blues – Basic Format
Use this basic format to play through a single round of the 12 Bar Blues. It is also very common for any song that extends into multiple instances of the 12 bars form to end on this basic structure.
12 Bar Blues – Repeating Format
Notice the change in the very last bar. When a 12 Bar Blues repeats several times throughout a song, it is typical for the 12th bar to end on a (V) chord. This is a “turnaround” and it really sets up the next instance of 12 bars so as not to repeat the (I) chord too many times in a row.
12 Bar Blues – Quick Change
The only difference in the Quick Change Blues format is in the second bar. A (IV) chord replaces the normal (I) chord. This gives the sound just a bit more variety rather than repeat the (I) chord for four straight bars.
Are you ready for the real deal? If so, check out the simplest of 12 Bar Blues rhythms. This is a basic 12 Bar Blues in the Key of E using two-note power chord shapes. While simple, it’s wildly popular in blues and rock music and is a favorite of musicians playing together at blues jams. And while playing full 7th chords is going to sound fuller, especially when playing on your own, most guitarists use these smaller versions of chords when playing rhythm in a band or jam situation.
If you’ve made it to the end of this blog, congratulations! You now possess some sound knowledge of the 12 Bar Blues and how it applies to blues and rock and roll music. With regular practice of the 12 Bar Blues in different formats and in different keys, you’ll be able to play along with friends and your favorite blues and rock songs. Good luck!