• # Chord alterations, “add X,” half diminished 7 chords, and more…

Here is a question that came in from Chris Myhre:

Flat 9, flat 5, flat 7th… this stuff is confusing — and for that matter the ADD 9, ADD 5, ADD 6, and the #9, #5 as well.  I guess I should also throw in the half-diminished chords, whatever those are.  I’m still trying to figure it out.  It all sounds beautiful but it seems that a #9 would be a minor note and a flat 7th is still just a regular 7th.  It’s hard to understand why the notation has to be so complicated.  Maybe things will become more apparent as I go along and learn more.

Anyway, I hope to understand more of this as I go along and I appreciate what you have done.  God bless,

—————–

Hi Chris,

It is understandable why you would be confused as some of the upper level courses just tell you what they are rather than covering their construction from the beginning (that’s for the 300pg course and the starter stuff to cover, which do a fine job btw).

Flat 7th just let’s you know to take the natural 7th (which is B in the key of C) and flat it one half step. If I just said “7,” you should automatically think B, not B flat. But the minute we say “flat 7th” then that means take the 7 and flat it (lower it) a half step… aka, “dominant 7th” or “minor 7th.”

Knowing numbers is crucial. It’s probably the best thing you can learn. Knowing your scales as numbers.

9 is basically the 2nd tone of the scale
11 is basically the 4th tone of the scale
13 is basically the 6th tone of the scale

How are they determined?

Just number your scale up two octaves

C = 1
D = 2
E = 3
F = 4
G = 5
A = 6
B = 7
C = 8
D = 9
E = 10
F = 11
G = 12
A = 13
B = 14

But if you think about it, D is 9 (sure enough when playing extended chords) but the shortcut is to just immediately think “2” (but up an octave usually). Same with the 11th, which is the 4th, and the 13th which is essentially the 6th.

When you’re instructed to “add 9,” that’s basically what you’re doing. You’re taking the original chord and adding whatever the 9th tone of the scale is. That’s it. Same with 13 or 6 or 2.

As for the “alterations,” (b9, #5, etc)… just like you flat the 7th tone (per the instructions above), you do the same with the 9th and other extended tones. Very simple. So if I’m in the key of C and instructed to play a b9 (aka – “flat 9”), I would first determine my 9th tone (D), and then lower it one-half step to Db. NEVER CHANGE THE ALPHABET LETTER when you’re doing this. For example, if I used C#, I would no longer be flatting the “9th tone” — instead I’d be raising the 8th tone (C) to C#, and that’s not what the instructions call for. So keep that in mind.

Also, yes, sharping the 9th tone is like playing a minor chord. But the big difference is that you cannot call it a minor chord because it still may be a major or dominant chord. In other words, a C7 #9#5 may still have an “E” in there (which makes this chord either major or dominant). What we are doing is essentially adding the 9 and then sharping it. So it’s giving you a chord with both a major third “E” and a “D#” (which isn’t quite a minor third because if you understand theory, that would be called an augmented second if it were played in the lower octave). So that’s why you need the alterations. Sometimes, though, you can just say “augmented” instead of #5… this is a case where sometimes they are pretty much synonyms. But be careful.

Let’s move on to your question about the “half diminished seventh” chord. But first, let’s back up and cover a more common chord first. This will help us to lead to the construction of the half-diminished seventh chord.

A diminished seventh chord is basically constructed of 3 minor third intervals.

It is important to note that:

Major third intervals have 4 half steps (like from C to E)
Minor third intervals, on the other hand, have 3 half steps (like from C to Eb)

You basically construct a diminished 7th chord by taking 3 minor thirds and piling them on top of each other…

C# to E is a minor third.
E to G is another minor third.
G to Bb is another minor third.

C# E G Bb would be a C# diminished 7 chord, for example.

For a lesson on why I used the notes above to name this chord, visit this link (you will use a mixture of sharps and flats for chord like this… see details at the link above).

Now, this leads me to the half diminished 7th chord.

The only difference is that you are taking the last “minor third” in the equation and making it a major third (which means you need to make it bigger by one half step since major thirds have 4 half steps in them). So instead of playing Bb, you’ll be playing “B.” Thus – C# E G B.

A half-diminished 7 chord is basically the same as a minor 7th chords with a flat 5 (aka – “min7 b5”). This is another way to look at half diminished 7th chords — just take a regular minor 7th chord, locate the 5th tone of the scale and lower that tone a half step.

Whewww! My fingers are tired.

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#### Jermaine Griggs

Founder at HearandPlay.com
Hi, I'm Jermaine Griggs, founder of this site. We teach people how to express themselves through the language of music. Just as you talk and listen freely, music can be enjoyed and played in the same way... if you know the rules of the "language!" I started this site at 17 years old in August 2000 and more than a decade later, we've helped literally millions of musicians along the way. Enjoy!

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