12-bar blues: chord pattern and how to play it
The 12-bar blues is a 12-measure chord pattern built on the I, IV and V chords. The basic form is I I I I, IV IV I I, V IV I I, usually played with dominant seventh chords and a shuffle feel. It is the base of countless blues, rock and jazz tunes.
The 12-bar blues is one of the most useful patterns in all of popular music. It is a chord progression 12 measures long that repeats again and again while a singer or soloist makes up new words or melodies on top. Once you know it, you can join in with blues, early rock and roll, boogie-woogie and a lot of jazz.
The whole pattern uses just three chords. If you already know how Roman numerals work in chord progressions, you will find this page easy. If not, the short version is that I means the chord built on the first note of the key, IV means the chord built on the fourth note, and V means the chord built on the fifth.
What is the basic 12-bar blues pattern?
Count the measures in groups of four. The first four measures stay on the I chord. The next two move to IV, then two return to I. The last four go V, IV, I, I. Each Roman numeral below stands for one measure.
| Line | Measure 1 | Measure 2 | Measure 3 | Measure 4 |
|---|---|---|---|---|
| Line 1 | I | I | I | I |
| Line 2 | IV | IV | I | I |
| Line 3 | V | IV | I | I |
In the key of C, I is C, IV is F and V is G. In the key of A, I is A, IV is D and V is E. The shape is identical, only the chord names change.
What does the 12-bar blues look like in C?
Here are the twelve measures in C, written as dominant seventh chords, each lasting one whole measure of 4/4. The pattern is split into three lines of four measures so you can see the structure.
Why are the chords dominant sevenths?
A dominant seventh chord is a major triad with a lowered seventh added. C7 is C, E, G and B♭. Blues players use this sound on I, IV and V alike, even though in classical harmony only the V chord would normally get a seventh. The result is the bluesy, slightly unresolved color that defines the style. The note B♭ also belongs to the blues scale, which you can learn on the blues scale page.
You do not have to play full sevenths. Beginners often play plain major chords, or just the root and the seventh as a two-note shape. All of these fit the same 12-bar frame.
What is the quick change?
A common variation is the quick change, where measure 2 goes to the IV chord instead of staying on I. The form becomes I IV I I, IV IV I I, V IV I I. It adds a little movement early and makes the form feel less static. Many players use it automatically. There is no rule, so both versions count as 12-bar blues.
| Version | Measures 1 to 4 | Measures 5 to 8 | Measures 9 to 12 |
|---|---|---|---|
| Standard | I I I I | IV IV I I | V IV I I |
| Quick change | I IV I I | IV IV I I | V IV I I |
| V V ending | I I I I | IV IV I I | V V I I |
The third version in the table has V for two measures in a row instead of V then IV. You will also hear it, especially in older recordings. Different bands and players pick their favorites, so do not worry that these differ.
What is a turnaround?
The last two measures of the form are called the turnaround. They bring the music back to the start so the next chorus can begin. Often the final measure plays the V chord, which creates a small question that the I chord at the top of the form answers. Players mark this with a lick or a short walking bass pattern. A simple turnaround is I in measure 11 and V in measure 12.
What is the shuffle feel?
Most blues is played with a shuffle or swing feel. Instead of dividing each beat into two even eighth notes, you divide it into a long note followed by a short one, in a pattern of 2 to 1. You can think of it as counting in triplets and skipping the middle one: one-and-a, two-and-a. Written music often notates this as straight eighth notes with a note that says swing, or as 12/8. See 12/8 time for how that count works.
How do you play the 12-bar blues on piano or guitar?
- Choose a key, such as C or A, and find its I, IV and V chords.
- Play the basic form with simple chords, one per measure, and count four beats in each.
- Switch the chords to dominant sevenths once the changes feel automatic.
- Add a steady rhythm, such as a shuffle with the left hand on piano or a palm-muted pattern on guitar.
- Play the notes of the minor pentatonic or blues scale over the top and make up short phrases.
Practice tip: sing the form out loud as you play. Say I-I-I-I, IV-IV-I-I, V-IV-I-I. If you lose your place in the 12 measures, the count will bring you back.
The 12-bar blues also works well for learning about the minor pentatonic scale, because that scale fits over all three chords. Many students learn the form first and then spend years finding new things to play on top of it.
12-bar blues in common keys
Check yourself
1. How many measures long is the standard blues form?
Answer: 12. The name says it: 12 bars, or measures, in three groups of four.
2. Which chords make up the blues in C?
Answer: C, F and G. I, IV and V in the key of C are C, F and G.
3. What are the last four measures of the standard form?
Answer: V IV I I. Line three of the form goes V, IV, I, I.
4. What is the quick change?
Answer: Measure 2 goes to IV. The quick change replaces the second I with IV, giving I IV I I.
5. Which type of chord is most common in the blues?
Answer: Dominant seventh. Dominant sevenths on I, IV and V give the blues its characteristic color.