Chord enrichment, by adding the natural extensions such as the ninth, the eleventh and the thirteenth. Enrichment of the seventh chords by adding the three natural extensions of the chord. For each kind of the seventh chord, there are enrichments that we call extensions. They are: the ninth, the eleventh and the thirteenth. In the major seventh chord, the ninth is always major, here the D note is added above the seventh B, the eleventh is always rised, we add the F# here, above the ninth, and the thirteenth (La) is major, added above the augmented eleventh F#. In the minor seventh chord, the ninth is always major, the D note, the eleventh, or the fourth of the this chord, is perfect, here the F note, and the thirteenth is major, the A note. In the dominant seventh chord, the ninth may be major (D), Minor (Db) or augmented (D#), the eleventh is augmented (F#), and the thirteenth is major, here the A note. In the half-diminished seventh chord, the ninth will always be major (D), the eleventh remains perfect (Fa), and the thirteenth may be major (A), and sometimes minor (Ab). In the diminished seventh chord, the ninth remains major (Re), the eleventh is perfect (Fa), and the thirteenth is minor (Lab), in order not to double the diminished seventh already in the chord, (A or Sibb).