12 Bar Blues Chord Progressions: No V7 in 12th Bar Type II(Dominant 7 & Minor)

12 Bar Blues (Quick Change, AKA Quick Four or Fast Four)

The red arrows in the diagram show where this differs from the standard 12 Bar Blues chord changes.

Roman Numerals in Diagrams represent chords in a key (or sometimes the root of the chord), based on the chords position in the key. We simply count the letters. So in C Major C=I, D=II, E=III, etc. Numbering is based on the major scale, so if a scale has a different note in comparison to the Major Key built on the same letter; we put a Sharp (♯) or Flat (b) in front of the Roman numeral to show how it differs from the major key. Then we put the symbol of the chords quality (i.e. Major, Minor, Dominant Seventh, etc.) after it. Once again, no symbol = Major.

Dominant Blues Progressions use Dominant 7th Chords

A Dominant Blues uses Dominant Seventh (7th) chords. Rarely do you hear them called Dominant 7th chords, though. Because a Dominant 7th chord is the most common form of seventh chord, we shorten the name to seventh chord.

So an A Dominant seventh chord is written A7, and pronounced either "A Seventh" or A "Seven". So your regular old 7th chord is really a dominant seventh. You could also have a Major Seventh, Minor Seventh, or Diminished Seventh chord (a half-diminished chord always has a seventh so we don't need to say "half diminished seventh").

Minor Blues Progressions use both Minor 7thand Dominant 7th chords

A minor blues uses primarily minor 7th chords. The last chord of a Blues chord Progression must always be a Dominant Seventh chord. There is a green box and arrow pointing to this in the chart on this page.

The Default Blues Progression is Dominant Not Minor

So when you hear "play a 12 Bar Blues" you assume it to be dominant, because its the most common type. See the 7th chord discussion above.