From: sumrn@dssv01.crd.ge.com (Robert N. Sum)
Newsgroups: alt.guitar
Subject: Re: forming chords (chord names repost)
Date: 12 Oct 92 13:16:48 GMT
Reply-To: sumrn@crd.ge.com
Followup-To: alt.guitar
Organization: GE R&D, DICE Program

In article <Oct08.030331.16731@yuma.ACNS.ColoState.EDU>,
braunste@fjord.ATMOS.ColoState.Edu (lance the braunstein) writes:
|>is there a systematic way to form a suspended (sus) chord?  for instance,  
|>is Asus4 simply an A with the 4th note moved up one?  also, i've seen  
|>people posting "+" chords - like B+.  what's up with that?  is it supposed  
|>to denote a sharp?
|>
|>steam

Though the following answers more than was asked, it seemed that it might be
appropriate to repost it as some of the responses have considered variations.
(I have cleaned up some of the misspellings from the last posting and added
a bit more on suspended chords.  Comments are welcome.)

I do not know of an official standard for chord naming, but the following
rules of thumb seem to be the most common for jazz and other popular guitar
work:

First, if we use C as the root (lowest or first) note of the chord,
then we have

  C  D  E  F  G  A  B  C  D  E  F  G  A  B  C
  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15

for the numbers of the notes.  If D is the root, then D would be 1 and so
on.

To get the qualities of the chord, we keep in mind the spacing between notes.
By half steps the notes are

  B#=C C#=Db D D#=Eb E=Fb E#=F F#=Gb G G#=Ab A A#=Bb B=Cb B#=C

where I've used equal signs to indicate notes of the same pitch.  (This is
important when naming chords, because the same chord can have more than
one name.)  The most commonly used chord qualities and their notations are:

  Quality			Notation

  major				M or blank or a small triangle,
  minor				m or - (minus sign),
  dominant seventh		7 (or greater odd number see below),
  diminished			superscript circle (^o here),
  half diminished seventh	superscript circle with slash (^o/ or ^o/7),
  fully diminished seventh	superscript circle 7 (^o7)
  augmented			+

The qualities arise from the exact spacing within the chord.  If we use the key
of C major then the basic triads (three note chords) are

C	C E G  (C to E is two whole steps, E to G is one and one-half)
Dm	D F A  (D to F is one and one-half steps, F to A is two whole)
Em	E G B
F	F A C
G	G B D
Am	A C E
B^o	B D F  (B to D is one and one-half steps, D to F is one and one-half)

and the seventh chords are

CM7	C E G B (major triad and major 7th)
Dm7	D F A C (minor triad and minor 7th)
Em7	E G B D
FM7	F A C E
G7	G B D F (major triad and minor 7th)
Am7	A C E G
B^o/	B D F A (diminished triad and minor 7th)

The fully diminished and augmented chords do not occur quite as naturally.
They require an altered scale such as the harmonic minor e.g., A harmonic
minor

 A B C D E F G# A

in which C E G# is C+ and G# B D F is G#^o7.  Note that the spacing on
augmented and fully diminished chords means that there are really only
4 and 3 unique chords of each type.  Voicing and key help define them.
In fact, they are often used to change key.

When naming chords larger than 7th chords, the odd numbers imply the
existence of all the lower notes.  For example, a G11 is G B D F A C
and a GM9 is G B D F# A.  To name chords, one keeps in mind the current
key or scale and the highest odd number used and adds the rest of
the notes in. However, in some cases this notation gets cumbersome
and there are some common shortcuts.  The most common one is to use
an even number in place of an odd number where there are "missing"
intermediates.  In the article by easteee@wkuvx1.bitnet,
the chords asked about can use the short cuts.

  1. A chord with the 2nd and 6th such as C E G D A has several names:

    Long name:  C add 9, 13
    Short name: C69

  2. A chord with just the 9 such as C E G D:

    Long name: C add 9
    Short name: C2

  3. Often, when one runs out of strings or fingers the 5 is just left out of
the voicing (consider the usual C7 chord on guitar--no G).  However,
if you really do not want a particular note, just put "no N", e.g., C E Bb

    C7no5

  4. If you want to alter a note such as C E Gb Bb, then

    C7b5

  5. The same goes for higher numbers, e.g., C E G Bb D#

    C7#9

  6. The example with 9th, 4th, and no 5th seems a bit unusual e.g., C D E F

    Could be:  C no5, add 9, 11
    or in Dm:  Dm9 no 5

I really need more context to figure out what this one is doing.

  7. One last fun thing are suspended chords where the 3rd is replaced with
either the fourth or the second.  For example C F G Bb would be

    C7sus4  or C7sus  (with the 4 implied)

  8. To suspend the second, you always use the 2 e.g., C D G

    Csus2

  9. In suspended chords, the suspension is often dependent upon the
context in which the chord is being used such as the key of the piece:
The suspension is not always one half step, but rather the substitution
of the third with the 4th (or 2nd) e.g., Amsus is A D E.  The vast
majority of the time, however, one can consider the suspension to be
just a half step above what would be a major third.

  10. Other than suspended chords, the 4th (or 11th) is not often used because
it can draw attention from the current key or scale to itself.  Therefore,
when it does appear it is often raised e.g., C E G Bb D F#

  C9#11

I think that this covers most of the common chords.  Enjoy!


-- Bob

==
  sumrn@crd.ge.com

  Robert Sum
  G.E. Corp. R. & D.
  P.O. Box 8, Rm. KW-C277
  Schenectady, NY 12301

  Tel. (518) 387-7696

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