Chordal extensions consist of different forms of the ninth, the eleventh, and the thirteenth and can be divided into two broad categories: diatonic and chromatic. Diatonic extensions enhance the structure of chords, whereas chromatic extensions modify that structure in a considerable way. The ninth has three distinct forms: a diatonic major 9th, a chromatic ≤9th, and a chromatic ≥9th. The eleventh has two forms: a diatonic perfect 11th and a chromatic ≥11th. The thirteenth has two forms: a diatonic major 13th and a chromatic ≤13t