Editing Extended chord (section)

==Chord structure==
[[File:Fifteenth chord from Schoenberg on C.png|thumb|Final chord of [[Arnold Schoenberg]]'s ''[[Sechs kleine Klavierstücke]]'', 2nd movement,<ref>{{cite book|last=Shawn|first=Allen|date=2003|title=Arnold Schoenberg's Journey|page=120|publisher=Harvard|isbn=9780674011014|quote=Technically a fifteenth chord}}</ref> in thirds: C–E–G–B–D{{music|#}}–F{{music|#}}–A{{music|#}}–C{{music|X}}. {{audio|Fifteenth chord from Schoenberg on C.mid|Play}}]]

Building on each of the major [[scale degrees]] the thirteenth chord [[Chord (music)|chord quality]] that is harmonic to such [[Scale (music)|scale]] (i.e. with all its notes belonging to such scale), results in the following table. The numbering is relative to the scale degree numbers of the [[major scale]] that has the major scale degree in question as [[Tonic (music)|tonic]]:

:{| class="wikitable"
|-
! Chord root !! Chord quality !! 1 !! 3 !! 5 !! 7 !! 9 !! 11 !! 13
|-
| '''I''' || IM<sup>13</sup> || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|natural}}
|-
| '''ii''' || iim<sup>13</sup>  || {{music|natural}} || {{music|b}} || {{music|natural}} || {{music|b}} || {{music|natural}} || {{music|natural}} || {{music|natural}}
|-
| '''iii''' || iiim<sup>7{{music|b}}9{{music|b}}13</sup> || {{music|natural}} || {{music|b}} || {{music|natural}} || {{music|b}} || {{music|b}} || {{music|natural}} || {{music|b}}
|-
| '''IV''' || IVM<sup>13{{music|#}}11</sup> || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|#}} || {{music|natural}}
|-
| '''V''' || V<sup>13</sup> || {{music|natural}} || {{music|natural}} || {{music|natural}} || {{music|b}} || {{music|natural}} || {{music|natural}} || {{music|natural}}
|-
| '''vi''' || vim<sup>7{{music|b}}13</sup> || {{music|natural}} || {{music|b}} || {{music|natural}} || {{music|b}} || {{music|natural}} || {{music|natural}} || {{music|b}}
|-
| '''vii{{music|dim}}''' || vii{{music|halfdim}}<sup>7{{music|b}}9{{music|b}}13</sup> || {{music|natural}} || {{music|b}} || {{music|b}} || {{music|b}} || {{music|b}} || {{music|natural}} || {{music|b}}
|}

Other thirteenth chord qualities do exist but they do not belong to any [[Musical mode|mode]] of the major scale. 

From the table it is clear that adding an eleventh or a thirteenth makes the seven chord qualities distinguishable from each other, as without an eleventh added the I and IV chord quality would be identical, and without a thirteenth added the ii and vi chord quality would be identical.