The most common four-note chord in most contexts, the dominant seventh chord shows up more frequently than either the diminished or the augmented triads, and likely the combination of the two. In the functional harmony heard in a lot of classical music, some folk, and some pop, the dominant seventh builds up tension before resolving to a major or minor triad a perfect fifth lower. This is most often heard in the V7-I progression, which serves a fundamental role in the harmony of Western notated music. Since the V is the dominant chord, this seventh chord has been called the “dominant seventh.” However, in the Blues, the dominant seventh chord is a whole different beast—every chord in many traditional Blues songs is some version of a V7, and here it contains no tension at all. The contrast between these two worlds is illustrated when kids add “and many more” at the end of “Happy Birthday,” which turns the properly-resolved tonic triad into a bluesy “dominant” seventh chord.
The Dominant Seventh
Symbols & Abbreviations:
Diatonic, Melodic Minor, Octatonic