Extensions and Tensions

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The basic tools of harmony are the triad and the seventh chord. Both structures are built in thirds or skips. This process uses the odd-numbered scale-degrees.

If this process is continued past the octave marker (scale-degree eight), with the scale being repeated at higher registers, then the odd-numbered tones nine, eleven, thirteen, fifteen, seventeen, nineteen, twenty-one, and twenty-three result. These tones are called scale extensions.

Like most chord tones, the tensions can be altered to fit the function, applying the formula change: b, #, bb, or in the case of 23rd chord extensions, (double-sharp).

The chord tones [1 - 3 - 5 - 7] and conventional tensions [9 - 11 - 13] are the typical tools of the American Musician. 23rd chord extensions are a logical outgrowth of the development of chromatic harmony in conjunction with jazz improvisational approaches involving a linear approach to chords [chord-tones and tensions]. This technique has been used in classical music and by some jazz improvisers, amongst them Eric Dolphy, David Murray, and Bruce Gertz.

Imaj7

1

3

5

7

9

#11

13

#15

#17

#19

b21

#23

example in C

C

E

G

B

D

F#

A

C#

E#

G#

Bb

D#

application

chord tones

conventional tensions

23rd chord extensions

IImin7

1

b3

5

b7

9

#11

13

#15

#17

#19

21

23

example in C

C

Eb

G

Bb

D

F#

A

C#

E#

G#

B

D

application

chord tones

tensions [ conventional 11 is natural ]

23rd chord extensions

V79, 13

1

3

5

b7

9

#11

13

#15

#17

#19

21

#23

example in C

C

E

G

Bb

D

F#

A

C#

E#

G#

B

D#

application

chord tones

conventional tensions

23rd chord extensions

IIm7b5

1

b3

b5

b7

9

11

b13

b15

17

19

bb21

b23

example in C

C

Eb

Gb

Bb

D

F

Ab

Cb

E

G

Bbb

Db

application

chord tones

conventional tensions [ can also take b9 ]

23rd chord extensions

Io7delayed resolution

1

b3

b5

bb7

9

11

b13

b15

17

19

b21

b23

example in C

C

Eb

Gb

Bbb

D

F

Ab

Cb

E

G

Bb

Db

application

chord tones

conventional tensions

23rd chord extensions

V7sus4

1

4

5

b7

9

#11

13

#15

17

#19

21

#23

example in C

C

F

G

Bb

D

F#

A

C#

E

G#

B

D#

application

chord tones

conv.

23rd

conv.

23rd

conv.

23rd ext.

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