A bit of Theory, 6 and 9 chords

[contiContiCONTI]

Hi guys,

Quick theory question that has been no my mind. Why is it that, for example, a C6 chord just has the three normal chord tones plus a 6 while a C9 chord has a dominant 7 note in it. They are written in the same way, shouldn't the C6 be written as Cmaj6?

When I see C6, I automatically think, C E G A (6th) A# (dominant 7th)

Thanks

[BriGuy1968]

Re: A bit of Theory, 6 and 9 chords

9 chords are a little different. When you are doing some variation of a 6 chord, it is always referred to as a 6. If we use a “C“ chord as the example, any time you add an “A” it will always be some variation of a 6 (depending on what other notes may be present).

To answer your question, it might be easier to compare a 9 chord to a 2 chord. In the key of “C“ both a 9 and a 2 are “D.“ The difference is that in a 9 chord we also add the seventh. Therefore…

C2 = 1 2 3 5
C9 = 1 3 5 b7 9
Cmaj9 = 1 3 5 7 9

- or -

C2 = C D E G
C9 = C E G Bb D
Cmaj9 = C E G B D

The reasoning behind it has to do with the overall structure. In a 2 chord we are simply adding the extra note (just like in a 6 chord), but in the 9 chord we are actually stacking 3rds.

Clear as mud, right? [emoji12]

[contiContiCONTI]

Re: A bit of Theory, 6 and 9 chords

9 chords are a little different. When you are doing some variation of a 6 chord, it is always referred to as a 6. If we use a “C“ chord as the example, any time you add an “A” it will always be some variation of a 6 (depending on what other notes may be present).

To answer your question, it might be easier to compare a 9 chord to a 2 chord. In the key of “C“ both a 9 and a 2 are “D.“ The difference is that in a 9 chord we also add the seventh. Therefore…

C2 = 1 2 3 5
C9 = 1 3 5 b7 9
Cmaj9 = 1 3 5 7 9

- or -

C2 = C D E G
C9 = C E G Bb D
Cmaj9 = C E G B D

The reasoning behind it has to do with the overall structure. In a 2 chord we are simply adding the extra note (just like in a 6 chord), but in the 9 chord we are actually stacking 3rds.

Clear as mud, right? [emoji12]

Ahhhh right that makes sense. So To get a C with the dominant 7th and the 6, it would be a C13?

[Mincer]

Re: A bit of Theory, 6 and 9 chords

Yes, you got it.

[eclecticsynergy]

Re: A bit of Theory, 6 and 9 chords

Never knew there was such a thing as a 2 chord, but that makes sense. I've always called it an add9.

[BriGuy1968]

Re: A bit of Theory, 6 and 9 chords

Never knew there was such a thing as a 2 chord, but that makes sense. I've always called it an add9.

Yeah, I actually usually call it an “add9” myself, but somewhere along the line I learned that there’s an official version.

I’ve also seen “add2.” The reality is that they’re all pretty interchangeable. Maybe add9 means adding the next “2” after the “5,” assuming the chord is built in ascending order?

Damn it... now my head hurts!

[gtrgrl]

Re: A bit of Theory, 6 and 9 chords

Soooooooo excited about the jazz!!!!

It was hard for me to understand a lot of the chord theory at first, but it really helped me understand how to use scales to improvise better.

I suck at jazz, but I keep learning. So many styles and so little time!!!

[eclecticsynergy]

Re: A bit of Theory, 6 and 9 chords

My favorite add9 is without the third. Just a really cool sound. The first one I learned was your basic cowboy A chord with the B string left open; I still use that one a lot in barre form.

One possible wrinkle I see in calling it a 2 chord is that in conversation it could (under certain circumstances) be confused with a diatonic ii chord.

[ItsaBass]

Re: A bit of Theory, 6 and 9 chords

A simple, boneheaded way to look at this is that the 9 is higher than the b7, but the 6 is lower than the b7.

Sounds utterly obvious and overly simplistic, but it's true when you look at how chords are formed: The answer really is that simple.

In building a 6th chord note by note from the root upward, the b7 is not "along the way" to the highest added interval in the chord (the 6). In other words, you're done forming the chord before you reach the b7 (1-3-5-6-done). But in a 9th chord, the b7 *is* "along the way" to the highest added interval in the chord (the 9). Moving up the intervals, you get to the b7 before the chord has been fully formed (1-3-5-not done yet so add b7-9-done). As you can see, it has a lot to do with what octaves you are using for the added notes, not just what notes they are. A 2nd chord does not contain all the same notes as a 9th chord, just as a 6th chord does not contain all the same notes as a 13th chord.

Bottom line that needs to be understood: The underlying "rule" to follow is not that the b7 goes into all them fancy chords with the extra numbers. The rule is that IF the fancy number tacked on the chord is higher than 7, THEN the b7 goes in.

Additionally, common ear sense regarding why you don't put a b7 into a 6th chord: It would be horrible sounding (for most purposes) for a chord to feature two adjacent notes within the same octave.

My favorite add9 is without the third. Just a really cool sound. The first one I learned was your basic cowboy A chord with the B string left open; I still use that one a lot in barre form.

One possible wrinkle I see in calling it a 2 chord is that in conversation it could (under certain circumstances) be confused with a diatonic ii chord.

With the 2 played, and no 3 in the chord, it is called a suspended chord. An add9 chord is a standard triad, with a high 2, but no b7. In other words, a 9th chord formed without stopping at the b7 along the way.