In jazz nomenclature these four traids would be indicated by the following symbols,
The seventh chords are extensions of these basic triad type. Chords C and Cm upon diminished triads. In example 2, we see the five most common types of seventh chords. Chords (a) and (b) are constructed upon major triads, (c) upon a minor triad, (d) and (e) upon diminished triads. The common chord symbols are indicated below each chord.
Others types of seventh chords are also possible, but are less common. Example 3 (a) shows a minor triad with a major seventh on top, 3 (b) illustrates a dominant seventh chord with a raised fifth, and 3 (c) shows a dominant seventh chord with a lowered fifth. Both 3 (b) and (c) occur in jazz as modifications of the basic dominant seventh chord.
Jazz also utilized so-called sixth chords. These chords are formed by the addition of an intervallic sixth above a basic triad type. Example 4 shows the two common sixth chords. Note that the sixth in both cases lies a major sixth above and the root of the chord. Since one of the chords is called major and the other minor, it is a common error to suppose that the sixth is altered to form the minor sixth chord.
Any seventh chord may be extended by the addition of ninths, clevenths, and thirteenths. For purpose of simpliecity the seventh chord types are listed below with the additions commonly found indicated alongside. Obviously, any note can be added to any chord. But in jazz, certain additions are common, while others are virtually never found. Note that regardless of the type of seventh chord the basic bibths, clevenths, and thirteenths found as additions stem from the major scale unless altered via a sharp or flat.