Seventh Chords
If you add a third to any triad, you obtain a seventh chord. This chord is called seventh chord because a seventh interval is formed in relation to the root.
Seventh chords may be built on each of the degrees of major and minor scales. Seventh chords may be identified by analyzing the triad and the seventh interval forming the chord.
The following examples show the structure and examples of the most common seventh chords:
Dominant Seventh: major triad, minor 7th
Half Diminished Seventh: diminished triad, minor 7th
Major Seventh: major triad, major 7th
Minor Seventh: minor triad, minor 7th
Diminished Seventh: diminished triad, diminished 7th