The Steel Guitar Forum

Trying to learn a little music theory and I have a question. Using the C Major scale as an example ( C,D,E,F,G,A,B, and C )with "C" being the root, "A" being the sixth note and "B" being the seventh, what is meant by the term ninth and thirteenth. Are these octaves of "D" and "A" ???

Jim Lawler wrote: Using the C Major scale as an example ( C,D,E,F,G,A,B, and C )with "C" being the root, "A" being the sixth note and "B" being the seventh, what is meant by the term ninth and thirteenth. Are these octaves of "D" and "A" ???

Yes.

"Ninth" can mean an interval or a chord.

OK, in a scale C D E F G A B C, The C is the root, or the key. The fourth is F, the fifth is G. Count from the first C, and the eighth is the higher C. The next note is D, which is the "ninth". If you play a chord using the C-E-G-C-D, you played a C major9th chord. Just like you play a 7th, which is C-E-G-B, that is a C major7th. Just music theory. C to C is numbered 1through 8. It is the same in any key, using the root as number 1.

This is just to add to the good info already provided by everyone else. Chords are usually built in 3rds. If you see the letter only, like "C", it means (C-E-G). When you refer to the major scale it's notes 1,3,5. If you see CM7, CMa7, CMaj7 or C with a triangle next to it, it means C major 7. Those all mean the same thing. That's (C-E-G-B). It's important to know that a C7 chord isn't the same thing. That actually means (C-E-G-Bb). Anytime you see a C7, C9, C11, or C13 it has the Bb rather than the B natural. Those chords are called dominant chords, and have a flatted 7th.

-Jeff

[quote="Jeff Valentine"]This is just to add to the good info already provided by everyone else. Chords are usually built in 3rds. If you see the letter only, like "C", it means (C-E-G). When you refer to the major scale it's notes 1,3,5. If you see CM7, CMa7, CMaj7 or C with a triangle next to it, it means C major 7. Those all mean the same thing. That's (C-E-G-B). It's important to know that a C7 chord isn't the same thing. That actually means (C-E-G-Bb). Anytime you see a C7, C9, C11, or C13 it has the Bb rather than the B natural. Those chords are called dominant chords, and have a flatted 7th.

-Jeff[/quote
something else to investigate is that some chords with extensions may be described in a couple of ways for example..
Altered,Augmented,sus,1/2 diminished,O or diminished etc or the number description #5#9 b5b9 etc

A Chord containing a *b7 plus a *6 qualifies as a 13th chord, where I come from; even if it doesn't contain the **9th!
B~*D~E~G#~B~*C#~E~G# = E13
E~*D~**F#~G#~B~*C#~E~G# = E9/13
(Whatever planet that is!)

Actually it's 2 scales bumped together with the first scale in the Mode your playing in and the 2nd scale is the major scale of the tonic of the Mode.
Example: C Dorian + C Major. Build the chords by starting on the tonic and go every other note etc..

C--D-Eb--F--G--A-Bb--C--D --E -F - -G - - A --B-C
1--2-b3--4--5--6-b7--8--9--10-11--12--13
1----b3------5----b7------9------11-------13

I also want to add, and hope not confuse you, that any chord you play, can be in one of 3 versions. Lets talk Cmaj again. It can be played C-E-G, OR E-G-C, OR G-C-E. And that goes for any key, with their respectful notes. (like the key of G. it is G-B-D, B-D-G, or D-G-B.) If you are playing just a 2 note chord, it is the 1 and 3, or the 1 and 5, of that chord, in most cases. Could be the 3 and 5. When you play the 1,3,5, and mash your AB pedals down, you go into the IV chord and it is the 5-1-3 of that chord. ( it still is the IV chord, but in the 5th position, musically). Then 2 frets up, with AB mashed, it is the V chord, 5th position.

Thanks for all the help guys. You have really cleared up a lot of my confusion. I am studying a C6th course and this will be a great benefit, especially about a C7th and a C Maj 7 being two entirely different chords. Thanks again.

Okay, here's another take on this "7th" question, remembered from simple theory from grammar school piano lessons. Forget about C7 in the key of C (the I7 is a very uncommon chord). Think about G7 in the key of C. The main chords in a key are the tonic, the subdominant fourth, and the dominant fifth. In the key of C that is the chords C, F and G. As often as not, the V (G) chord is played as the 7th, thus, the dominant 7th. The 7th of G7 is F, which is in the C scale. Thus, the most common 7th chord in western music is the V7, or the dominant 7th. It is a 7th chord that can be made entirely from the diatonic scale, no chromatics required, and it is the only 7th chord that can be made that way. The dominant 7th is the model for all 7th chords. Therefore, chords with a 7th a whole step below the upper root are called dominant 7th chords, although technically only the V7 is THE dominant 7th chord.

But that presents a dilema when talking about a 7th chord other than the dominant 7th (the V7). Generally the notes in a chord are not numbered after their degree in the key signature scale, but rather their degree in the scale of the root of the chord. From that standpoint, the major scale 7th is a half-step below the root. Therefore, it is called a major 7th, to differentiate it from the 7th used in the dominant 7th chord. The dominant 7th note is also called a minor 7th. It is a half-step below the major 7th, just as the minor 3rd is a half-step below the major 3rd interval. Also, since it is a half-step below the major 7th, it can be called a flat 7.

This seems to explain why the diatonic major scale 7th is called a major 7th, and the note a half-step lower is called the dominant 7th, minor 7th, or flat 7. And because it is much more common that the major 7th, it is assumed when anyone says merely "7th."

In terms of numbering the other intervals, they are most commonly added to a 7th chord. So, once a 7th is in the chord, the other numbers are added above the 7th. Thus, a 6th in a chord without a 7th is called a 6th, but in a chord with a 7th is called a 13th. Likewise, the 2 added to a 7th chord is called a 9th. In a chord without a 7th, it is called "add 2" (or sus 2). This doesn't mean you always have to play a 7th in a 9th or 13th chord. Someone else in the group is usually playing the 7th, so you can play the 9th (or 13th) and any other notes in the chord, with or without the 7th, and it is still a 9th chord (or 13th).

I think David has the right take.

David Doggett wrote:Generally the notes in a chord are not numbered after their degree in the key signature scale, but rather their degree in the scale of the root of the chord. From that standpoint, the major scale 7th is a half-step below the root. Therefore, it is called a major 7th, to differentiate it from the 7th used in the dominant 7th chord. The dominant 7th note is also called a minor 7th. It is a half-step below the major 7th, just as the minor 3rd is a half-step below the major 3rd interval. Also, since it is a half-step below the major 7th, it can be called a flat 7....
And because it is much more common that the major 7th, it is assumed when anyone says merely "7th."

And as much as I'd like to agree with Carl, and further see the M7 become the dominant 7th, it won't happen, and it's just as well.
Band terminology rules, and what's dominant dominates.

To make things simple for my guitar students I tell them that a 7th chord includes a note that is two frets lowere than its' name. G7 has an F, D7 has a C, E7th has a D...