The 12-Bar Blues and Dominant 7th Chords 

The 12-bar blues progression is a common musical form that is found primarily in traditional blues music as the name implies but has made it way into country and rock and roll as well. “Blues” music as a genre relies heavily on the use of Dominant 7th chords, and hundreds of popular songs are based on the “12-bar blues progression.” While the 12-bar blues progression largely stays the same, the keys can vary drastically from song to song. Now that we know how to play several common dominant 7th chords, we can learn the 12-bar blues progression in a variety of keys. 

The 12 bar blues progression uses 3 chords. Each chord is a certain distance apart from each other and is based on the major scale. Each chord of our 12-bar blues will use the 1st, 4th and 5th notes of the major scale as the roots for our dominant 7th chords. For example, in the key of G major, my 1st, 4th and 5th notes of the scale are G, C, and D respectively.  

To understand the placement of the root notes within the key, we use Roman Numerals to refer to the chords within the key. A chord based on the Root would be represented by the roman number “I” while a chord that is derived from the 4th note in the scale. would be represented by the roman numeral “IV.” Note the Major chords will have Uppercase numerals, and the Minor chords will have Lowercase numerals. 

This means that in the key of G, the root of the “1” chord is G, the root of the “IV” chord is C, and the root of the “V” chord is D. When they are played as dominant 7th chords (as would be appropriate in the Blues), the resulting chords would be the G7, C7, and D7 chords.

Using the chords from this lesson, the 12-bar blues progression can be played in 4 different keys: G major, D major, A major, and E major. The table below shows us how each of these keys uses each of the dominant 7th chords from this course.

Now that we understand how our chords relate to the root notes of our keys, we can play the 12-bar blues progression in each of these four keys. In the example below, you will see the form of the 12-bar blues in Roman numerals, by playing the correct chords for the corresponding Roman numerals, you can play this progression in the keys of G, D, A, and E. Be sure to practice this progression in all four keys, and memorize the sequence of the progression before moving on.