12 Bar Blues
Glenn Weiser

Every rock, blues, country, folk, and bluegrass musician should know the 12-bar blues in the seven most string-friendly keys. They are: A, B, C, D, E, F, G, and G. The flat keys other than F are most often used in jazz, and aren’t dealt with here. Blues is useful as the easiest way to jam when musicians have no other songs in common. It can be played with any groove, and is an ideal way to develop improvisational skills. Many famous American songs in every genre use this chord progression.

1. First, you need to know what the I, IV, and V7 chords are in each key. For this, memorize the chart below. The key is named after the I chord.

2. Below is the 12-bar blues pattern. Each of the three lines of the usual verse form (A-A-B) occupies four measures. Blues is played in 4/4 time (12/8 is really tripletized 4/4).
 

In the second bar, IV is often substituted for I in a variation called the “quick change.” In the eighth bar, V7 is sometimes used in place of IV (as in many Chuck Berry songs). In the final bar, V7 is usually used before a repeating a chorus-this called a “turnaround” -and I is used for the last chorus. Seventh chords can also be substituted throughout.

Minor key blues, which should also be learned, has a minor I and IV, and a dominant V7 as in major key blues.

3. 12-bar blues in 7 keys. These should be memorized.

In A: / A / A or D / A / A / D / D / A / A / E7 / D or E7 / A / A or E7 //

In B: / B / B or E / B / B / E / E / B / B / F#7 / E or F#7 / B / B or F#7 //

In C: / C / C or F / C / C / F / F / C / C / G7 / F or G7 / C / C or G7 //

In D: / D / D or G / D / D / G / G / D / D / A7 / G or A7 / D / D or A7 //

In E: / E / E or A / E / E / A / A / E / E / B7 / A or B7 / E / E or B7 //

In F: / F / F or Bb / F / F / Bb / Bb / F / F / C7 / Bb or C7 / F / F or C7 //

In G: / G / G or C / G / G / C / C / G / G / D7 / C or D7 / G / G or D7 //