12-Bar Blues Form

The 12-bar Blues is the most common form of the blues. The primary chords (I, IV, V) are the main chords to appear in blues.
Most typically, a 12-bar blues begins with the I, and the IV chord always appears on bar five. Many variations can occur. The chart below shows a master progression with some of these variations, which replace the existing measure(s) in the Primordial Blues.

**12-bar Blues progression**
examples in key of C
MEASURE NUMBER	1	2	3	4	5	6	7	8	9	10	11	12
PRIMORDIAL BLUES	I⁷ C⁷	I⁷ C⁷	I⁷ C⁷	I⁷ C⁷	IV⁷ F⁷	IV⁷ F⁷	I⁷ C⁷	I⁷ C⁷	V⁷ G⁷	IV⁷ F⁷	I⁷ C⁷	V⁷ G⁷
BUMP	I	IV⁷ F⁷	I	I	IV	IV	I	I	V	IV	I	V
# IV DIMINISHED SEVENTH	I	I	I	I	IV	#IV^o7 F#^o7	I	I	V	IV	I	V
SIMPLE TURNAROUND	I	I	I	I	IV	IV	I	I	V	IV	I⁷ IV⁷ C⁷ F⁷	I⁷ V⁷ C⁷ G⁷
HARMONIZED BASS-LINE TURNAROUND ascending	I	I	I	I	IV	IV	I	I	V	IV	I⁷ I⁷/_3rd IV⁷ #IV^o7 C⁷ C⁷/_E F⁷ F#^o7	I⁷/_5th V⁷ C⁷/_G G⁷
HARMONIZED BASS-LINE TURNAROUND descending	I	I	I	I	IV	IV	I	I	V	IV	I⁷ I⁷/_7th IV⁷/_3rd bVI⁷ C⁷ C⁷/_Bb F⁷/_A Ab⁷	I⁷/_5th V⁷ C⁷/_G G⁷

The 12-bar Blues is often played with a shuffle feel. Faster tempos see simpler changes, while slow blues can have more complexity. Extremely fast tempos can see the progression flatten out, with measures 9 and 10 both being the V chord, and measures 11 and 12 both being the I chord.