"Why" re: same chord, two names

David F.

I'm posting the question here because I do use the book mentioned.
This is probably more a general theory question but how does one chord end up with multiple names? I'm sure all of the more experienced guitarists than me can name examples. Thanks.

MichaelHorowitz

Hi David....because any given group of notes can be analyzed in numerous ways. For example the notes A C E could be an A minor chord or a C Maj 6 chord. Just depends on the context. A class in music theory would help you understand all the ways to analyze chords.

thanks!

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Buco

I'll try to expand on Michael's example. Everything in western music traces back to major scale, right? So taking major scales of the two examples:
A major scale notes are; A B C# D E F# G#
so A C E notes would make up Am cord, A as a root, C as a minor third and E as a fifth.
C major scale notes are; C D E F G A B
so A C E here would give you like Michael said CM6, in this case A as a sixth note, C as a root and E as a major third.
Makes sense? Important thing to note here is something I changed in my own thinking relatively recently after taking some music theory lessons myself is that your bass note in cord doesn't have to be root and when you make up a cord it doesn't always mean that your lowest note is root.

croth

I don't think you need to use 2 scales to explain this. As far as I can see, both the CM6 and Am7 can be derived from the one C-Major scale, which is all the white notes on the piano. Making chords from the one scale is called "harmonizing the scale".

The C Maj scale is C D E F G A B, as you stated.

If we build a a chord on the first note, C, it becomes C-E-G, or C Major. The chord built on the first note of a major scale is always a Major chord. We can add the 6th note, A, for color. This turns the CMaj into CMaj6, or C6 for short and that is spelled C-E-G-A.

What happens next is that sometimes the 5th of the chord is dropped (in this case the G) and we end up with just C-E-A.

Moving along, the chord built on the 6th note of a major scale is always a minor chord. In the C scale, the 6th note is A. When we build a chord on the A, we end up with A-C-E, also known as Am. We can add a 7th note to a minor chord for color and create an Am7. This chord is spelled A-C-E-G.

It becomes too complex to explain why these notes are used to build chords (it has to do with major 3rds and minor 3rds) but you can see that C-E-G-A, or C6, uses the same notes from the C Major scale as does the Am7, which is spelled A-C-E-G. The two sets of notes are in a different order, but they are the same 4 notes, yet you get two different names from them.

One of the most interesting examples of this multi-name phenomenon exists in a 4 note chord often called a m7b5. Let's use Em7b5 as an example. This same chord can have at least 3 names: Em7b5, Gm6, C9. There may be a 4th name but I can't come up with it now if there is. It might be E half-diminished but let me not push my luck.

It takes a lot of words to explain a simpler concept, but I hope I've cleared the waters for you and not muddied them further.

Jazzaferri

Actually if my memory hasn't gotten the worse of me the correct name for chords that come from the notes of a given scale is diatonic. The diatonic triads (3 note chords) of C major scale (all white keys on a piano starting on C) starting on the tonic are 1 - C major 2 D minor 3 E minor 4 F major 5 G major 6 A minor 7 B diminished and back to C major an octave up.

The notes of the C major triad can also be played E,G,C(octave) which is the first inversion and G, C, E which is called the second inversion. And so on for all the triads.

If one adds an interval of a third (remaining diatonic) on top of each of those triads one ends up with the following diatonic 7th cords in C major

1 Cmaj7 2 Dm7 3 Em7 4 Fmaj7 5 G7(dominant) 6 Am7 7 Bm7b5 (half diminished).

Each of these chords can be played in 3 inversions.

Once one starts to drop the 5th or the tonic (or both) which is often done and considering relative minors the same 3 or 4 notes could be named differently depending on the harmonic context as was pointed out above. One of the best books for those starting out and is clear concise and understandable is called "A Player's Guide to Chords and Harmony" by Jim Aiken. I don't know if Michael has it in the store but very very worthwhile.

andmer

good download in this thread.
viewtopic.php?f=16&t=7068

dennis

Buco wrote:

I'll try to expand on Michael's example. Everything in western music traces back to major scale, right? So taking major scales of the two examples:
A major scale notes are; A B C# D E F# G#
so A C E notes would make up Am cord, A as a root, C as a minor third and E as a fifth.
C major scale notes are; C D E F G A B
so A C E here would give you like Michael said CM6, in this case A as a sixth note, C as a root and E as a major third.
Makes sense? Important thing to note here is something I changed in my own thinking relatively recently after taking some music theory lessons myself is that your bass note in cord doesn't have to be root and when you make up a cord it doesn't always mean that your lowest note is root.

Hi Buco, I don't want to be nitpicky or offend you, but there are a number of serious mistakes in your example

the Am chord is completely unrelated to the key of A MAJOR...

in the key of C, the notes A C E don't make up a C6, they make up a plain ol C major chord..... Of course, it *can* be a C6 depending on how you use it, but in your example, it's really just a plain C chord...

tacosandbeer

dennis wrote:

Buco wrote:

I'll try to expand on Michael's example. Everything in western music traces back to major scale, right? So taking major scales of the two examples:
A major scale notes are; A B C# D E F# G#
so A C E notes would make up Am cord, A as a root, C as a minor third and E as a fifth.
C major scale notes are; C D E F G A B
so A C E here would give you like Michael said CM6, in this case A as a sixth note, C as a root and E as a major third.
Makes sense? Important thing to note here is something I changed in my own thinking relatively recently after taking some music theory lessons myself is that your bass note in cord doesn't have to be root and when you make up a cord it doesn't always mean that your lowest note is root.

Hi Buco, I don't want to be nitpicky or offend you, but there are a number of serious mistakes in your example

the Am chord is completely unrelated to the key of A MAJOR...

in the key of C, the notes A C E don't make up a C6, they make up a plain ol C major chord..... Of course, it *can* be a C6 depending on how you use it, but in your example, it's really just a plain C chord...

Wow! If you're going to be 'nitpicky', in the key of C the notes A C E make up an A minor triad, not a 'plain ol C major chord'. What's up with that bit of misinformation.

jovation

f I may add some input based on my understanding.

Depending on whether you refer to classical music or jazz music theory, you can get different
answers to the question.

Jazz theory talks about one chord having two names, as a because it defines the idea of a chord
differently. Being improvisational in nature, the player is considered to have certain musical
freedoms. So, a C6 chord and an Am7 chord are called the same chord, because
they share the same note pitches in the chord (C, E, G, A), and the order of the notes are
not important in terms of what you wish to call the chord you are playing.

Classical theory does not say C6 and Am7 are the same chord. They are two chords which
are enharmonically equivalent..that is, they produce the same pitches. This is no
different than saying F# and Gb are two different names for the same note.

Jazzaferri

Re-reading this thread is it any wonder that lots of people find music theory ... which is a poor english way of describing our pathetic attempts at using words to describe music .... confusing :shock:

Bones

Serously! I think I'm getting a headache!