In this, the first of four videos on how to play over a dominant seventh chord, you take a look at where a dominant seventh chord comes from and its natural scale, the dominant scale.
The dominant seventh chord is drawn from the 5th degree of the major scale. When you build a triad from the 5th degree of a major scale, you get a root, 3rd, and 5th. For example, in the D major scale the triad built on the 5th degree is A-C#-E, which makes an A major chord.
When you add a 7th, you get a flattened 7th, also called a minor 7th. Using the D major scale again, but counting from its 5th degree, A, the 7th is G. A-C#-E-G makes an A7 chord.
This unique combination of a major triad with a minor 7th only naturally occurs on the 5th degree of a major scale. In music theory each degree of the major scale has a name. The 5th is called Dominant, so its 7th chord is called dominant seventh.
When you play over any type of dominant seventh chord, the most natural scale to play is its parent major scale. With A7, for example, the scale to play is D major, since A7 is drawn from that scale.
Although you’re using notes from the D major scale, you really hear it as being a type of A scale, since the root of the A7 chord, A, sounds like your tonic pitch, or starting point. When you use a major scale, but center on its 5th degree, it’s called Mixolydian mode. The dominant scale is really a mode, Mixolydian, which is based on the 5th degree of the major scale. You can play A Mixolydian mode, also known as the A dominant scale, by using D major scale patterns, but centering your playing on A instead of D.
About the Educator & Series
Desi Serna is the author of Fretboard Theory and
In this series of four, free