Extended chords


What's up guys.
Can anyone tell me where to find the chord formulas for extended and altered chords? I want to learn how to construct chords like b9's, 11's, 13's etc. I want to add some of those Hendrix type chords to the repetoire. I looked all over the usual lessons sites, but nobody has the formulas that shows how to build them. ex. (1, 3, 5, b7)


Mark C

Extensions are intervals + 7. For instance, the 9th is the second scale degree (of a major scale), the 11th is the fourth, and the 13th is the sixth. Almost always voiced as one of the two highest sounding notes in the chord. In addition, it's only an extension if it does not replace the third or the seventh of the chord. So a chord with no seventh scale degree and an added sixth is called a sixth chord, whereas a chord with a seventh scale degree and an added sixth is called a thirteenth. If this is still confusing, feel free to ask any questions and I'll try to answer them.


Just look at it like this...all chords with numbers in them have all the odd numbers in them up until the highest number mentioned in the chord. Does that make any sense? Hmm...ok, check it out:

Cmaj13.........1,3,5,7,9,11,13 (although the 11 is usually left out here)

BTW....this is just a C scale stacked in thirds.




Great succinct explanation MtFingers.

A little history and further explanation.

In baroque music theory chords are built on intervals of a third.

minor 3rd = three 1/2 steps

e.g. C to C# to D to Eb

There are three 1/2 steps going from C to Eb; AKA minor 3rd

Major 3rd = four 1/2 steps

e.g. C-C#-D-D#-E

There are four half steps going from C to E; AKA a Major third

To build triads use thirds:

minor chord = a minor 3rd plus a Major 3rd

e.g. C-Eb-G (C to Eb is a minor 3rd and Eb to G is a Major third)

Major chord = a Major 3rd plus a minor 3rd

e.g. C-E-G (C to E is a Major 3rd and E to G is a minor third)

In the Baroque period, most chords were three or four notes if you include an octave.

The dominant 7th chord was also used during the baroque period for cadences:

It's called a dominant 7th because in baroque music it was the dominant (fifth) chord of the scale that added an extra note.

Only the dominant chord could have a minor 7th note added to it and even then it was only aloud in cadences. (There are some exceptions to this when you get into neapolitan 6th chords.)

It's called a 7th chord because it adds a note seven steps away from the root of the chord. i.e. G-F = a minor 7th

In the key of C the fifth (dominant) chord would be G. If you build a G chord in thirds in the key of C (no sharps or flats) you get:

G-B-D-F (Major 3rd + minor 3rd + minor 3rd)

The F is a minor 7th away from the root note G. The F note had a strong pull to the root as well as to the third of the TONIC chord (C chord in this example) which is why it was used in cadences.

This was pretty much the law up until Satie, Debussy and Ravel started stirring things up with 6th, major 7ths, 9ths, whole tone scales and such.

I'm pretty sure this is where the term EXTENSIONS came in because the jazz guys who dug the Impressionists extended the baroque three note chords by piling more thirds on top of the triads as MtFingers & Mark point out.

Today we call any chord a Dominant 7th if its built M3+m3+m3 no matter where it falls in the scale but baroque music has very specific rules.

If you sit down at a piano, it's much easier to visualize. Just play every other note.


Hey, that's damn cool, Old Tele Man! I hadn't thought of them that way before.

Time to work on my chord progressions, then. :cool:

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