Understanding Dominant Chords

Dominant chords are like Major chords (135) that have a flattened 7th (b7) added to the 135 chord formula (135,b7=dominant 7th). So, if a C Major is C(1) E(3) G(5), we add a Bb (flattened 7th note of the C Major scale). Then, depending on which dominant chord you want, you simply add that note to the 7th chord:
  • Dominant 7th-135b7
  • Dominant 9th-135b79 (add the 9th to the dominant 7th formula)
  • Dominant 11th-135b7911 (add the 11th to the dominant 9th formula)
  • Dominant 13th-135b791113 (add the 13th to the dominant 11th formula) 
Notice that dominant chords are only 7, 9, 11, 13. Also notice that each successive dominant chord has exactly the same formula as the previous chord, but with the new 'chord name' note added. (For example, dominant 11 is same as dominant 9 -1 3 5 b7 9, but we add the 11.)

We don't need to try to play every note in the chord. In the case of 11 the 9th isn't as important, and in 13 the 11th isn't as important. The important notes are clearly root (as a tonal centre), 3rd (to sound major) b7 (to have 'dominant/bluesy' sound), and 11th to add that colour tone that gives the chord it's name.

When playing any chord voicing, work-out which note is which chord tone. This will not only help you to understand the relationship between modes and chords, but also increase your knowledge of the notes on the guitar neck.