Dominant Seventh Chord

In music theory, a dominant seventh chord, or major minor seventh chord, is a chord composed of a root, major third, perfect fifth, and minor seventh. It can be also viewed as a major triad with an additional minor seventh. It is denoted using popular music symbols by adding a superscript "7" after the letter designating the chord root. The dominant seventh is found almost as often as the dominant triad. In Roman numerals it is represented as V7. The chord can be represented by the integer notation {0, 4, 7, 10}.

Of all the seventh chords, perhaps the most important is the dominant seventh. It was the first seventh chord to appear regularly in classical music. The name comes from the fact that it occurs naturally in the seventh chord built upon the dominant (i.e. the fifth degree) of a given major diatonic scale. Take for example the C major scale (C, D, E, F, G, A, B, C):

The note G is the dominant degree of C major - its fifth note. When we arrange the notes of the C major scale in ascending pitch and use only these notes to build a seventh chord, and we start with G (not C), then the resulting chord contains the four notes G-B-D-F and is called G dominant seventh (G7). The note F is a minor seventh from G, and it is also called the dominant seventh with respect to G. However, the 'dominant' seventh is used on notes other than the dominant, such as the subdominant.