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I have very little knowledge of music theory (enough to know what's the major scale and how to find the major chord of a note) but I know a good number of chords by name and could figure out the ones I don't know based on the patterns.

Meaning that even though I could give you the C suspended 4th chord, I still have no idea what the name means.

I was once told that the names are based on the position of its notes on the major scale (like themajor chord is the 1st, 3rd, and 5th), but a C7 has a Bb in it, while the 7th note of the C major scale is B.

Can someone explain at least how the common names are defined?

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C7 actually has Bb in it (not A#). Yes, it's the same note, soundwise, but it comes from the 7th note being flattened. 7th note = B, so 7th flat = Bb. –  Tim Aug 16 '13 at 8:28
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Let's take Tim's major scale as a starting point and build diagrams from there. This will get heavy beyond 7 chords, but they're intermediate/advanced so I may need correcting by some jazz experts!

taking 1 as the Root of the major scale, and each number representing the degree of the major scale. so 1 3 5 = the 1st, 3rd and 5th notes of the major scale.

b=Flat, #=Sharp

Chord Formulas


Triads

Major: 1 3 5

Minor: 1 b3 5

diminished: 1 b3 b5

Augmented: 1 3 #5

sus2: 1 2 5

sus4: 1 4 5


7 Chords

7 or Dominant 7: 1 3 5 b7

maj7: 1 3 5 7

min7: 1 b3 5 b7

diminished 7: 1 b3 b5 bb7 (note that all 3 non root notes are diminished/flattened) half-diminished 7: 1 b3 b5 b7 minor/major7: 1 b3 5 7

See also: Wiki on 7ths


5:1 5 (also known as a power chord)

6: 1 3 5 6

min6: 1 b3 5 6

add 9: 1 3 5 9

add 11: 1 3 5 11

add 13: 1 3 5 13

9: 1 3 5 b7 9

11: 1 3 5 b7 9 11 13

13: 1 3 5 b7 9 11 13


Beyond that is starts to get complicated

You can combine the names of the basic triads with the later chords to spell even more, for example: augmented add 9 = 1 3 #5 9

and you can apply the naming of 7 chords to 9, 11 and 13 chords, for example Maj9 = 1 3 5 7 9 dim9 = 1 b3 b5 bb7 9 (note that 9 is not diminished!)

This gets a little tricky, but when naming tones with a 7 you do it per tone, for example

7/6 = 1 3 5 6 b7 7/#9 = 1 3 5 b7 #9 7#9b13 = 1 3 5 b7 #9 11

Also, remember that 9, 11 and 13 can also be thought of as 2, 4 and 6, so 7/6 = 1 3 5 6 b7 could be writtten as 7 add 13: 1 3 5 b7 13

I'm going to hold it there, because to be honest those last 4 lines took about 2 hours of research to confirm, because I know the theory but I'm not in a place where I use them regularly yet.

Perhaps someone else could clarify how you would write a chord that's a diminished triad, but with a 7, 9 etc on top, so 1 b3 b5 7, because I couldn't find anywhere mentioning the theory and a chord namer just listed it as Cmb5 maj7.


On Sus chords the simple definition is that a sus chord is a chord with the 3rd moved to either the 2nd or the 4th, but the full story gives a wide picture of where it came from and how to use it.

A suspended chord is the modern result of what is called a ligature, originally it was when you held on to a note from the previous chord and delayed it's resolution. In a sus 4 chord you have a tension between the root and the 4th that traditionally would then resolve to the 3rd, like so

Sus4 example

Over time the sus chord became a chord in it's own right rather than as a passing chord. It's still very common to resolve a sus chord, as in the ever popular D - D sus pattern on guitar but it's also got a life of it's own in other places.

The default sus chord these days is a sus 4 chord, so when you see sus on it's own it means sus 4, and sus2 will be named sus2.

Also, for a fantastic reference on chords and their use in progressions(especially for guitarists) check out Ted Greene's Chord Chemistry

Hope that helps!

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That was pretty much what I was looking for! I just got my guitar back from repair and I'll go through this tonight to understand them better! Thanks! –  Gabe Aug 16 '13 at 20:26
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Given time, Csus4 will be known as C4, and Csus2 as C2.If they're'add 2' or 'add 4' write it. Otherwise what else could they be? –  Tim Aug 16 '13 at 21:08
    
Please check the minor 6th. Should it be 1-b3-5-6. It's a minor triad with a major 6th note added. –  Tim Aug 16 '13 at 21:11
    
Good spot Tim, my bad –  Alexander Troup Aug 17 '13 at 8:52
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It's pretty interesting how the diminished 7th is 4 diminished chords in one. I have a question though. Why is the 7th flatted twice instead of once? –  Caleb Sep 12 '13 at 3:14
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All chords have the major scale (Ionian mode) as their starting point. They are based on the root note of that scale, giving the chord name, e.g. C maj. has C as a base (and usually) bass note. A basic chord will then follow notes 3 and 5 of that scale. E.g. C - E and G.

To make a chord minor, the 3rd. is flattened, as C - Eb - G. Chords which have a number after them use that number note as well, as C6 = C-E-G-A. This is complicated by the fact that there are 3 7ths and 3 9ths.The 7ths are Cmaj7 C-E-G-B., Cmin7 C-Eb-G-Bb and C dominant 7 C-E-G-Bb. You can also find a Cmin/maj7th, played with C-Eb-G-B. The 9ths are bigger versions of 7ths, in that they have the 9th note from the scale as well.

Sus chords are just what they say - the 3rd note is suspended and either a 2nd or 4th note substituted instead. So they're neither maj. or min. If a chord has the 2nd or 4th as well, it's called 'add 2', or 'add 4'.

This is just a basic answer, which obviously will translate into each and every key, once the scale notes are known. Bear in mind that an altered note keeps its letter name; a flat 5 of C is Gb, it can't be called (or written) F#, even if the sound is the same. That keeps chord names easier to make sense of.

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One step at a time:

First off, most chords are built on a "triad"; a set of three pitches, with a predefined interval between each of them, beginning at a specific note. This beginning point is called the "root" of the chord, and it is the note for which the chord is named. This is not always the note on the "bottom" of the chord; we'll explore that later.

For instance, a "C" chord will have, as its root note, a C. The chord's name and quality are the same regardless of which octave, or how many, are present in the notes played.

Now, the triad, built on the root, will have predefined intervals between the three primary notes of the chord, which when based on a particular root, will determine what those actual notes are and what the resulting "quality" of the chord will be.

The most basic triad quality is "major". Major chords have, as their defining tonal characteristic, a "happy" sound. The major triad is composed of the root, then the note a "major third" (two "whole steps") above it, and then the perfect fifth (which is a "minor third", a step and a half, above the second note of the triad). A C major triad (simply labelled "C") is composed of the notes C, E, and G, which are, for the same reasons, the first, third and fifth notes of the C Major scale.

The next most common is the "minor" triad. Minor chords have the same root and perfect fifth, but the middle note, the third, is lowered by one half step. This makes the interval between the root and the third a "minor third", meaning the interval between the third and fifth is now "major" (because that is as I said the same note). Minor chords, compared to major chords, are generally described as sounding "sadder". A C minor triad (labelled "Cmin" or "Cm") would be composed of C, Eb, and G.

After that, the last "natural" triad (composed of three notes, each separated by two "scale degrees" from their neighbors) is the "diminished" triad. This occurs naturally in the major scale when you take the seventh, second and fourth scale degrees as a triad; both of the intervals between the three notes end up being minor, so not only is the third lowered by a half-step, but so is the fifth. Diminished chords are generally described as sounding "dark" or "sinister"; many of the cliche examples of organ music the bad guy would typically be playing, like Bach's Toccata in D and the theme to Phantom of the Opera, have a lot of diminished chords. A C diminished triad (Cdim) would be composed of C, Eb and Gb.

There are other possible triads. The most common "altered" triad is the suspended triad. Instead of using the third scale degree as the middle note, you use the fourth. This is a very powerful chord, because it contains all three of the notes in a major key from which you can form a major chord by using it as the root, and it also sounds like it "wants" to resolve to the major triad. A C suspended triad (Csus, sometimes Csus4) is C, F and G

Beyond triads, many chords commonly used in modern music add additional notes to the triad to form a four-note chord. The most common note to add is the seventh scale degree, however it is typically lowered by a half-step to produce the "minor" or "dominant" seventh. A C dominant seventh chord (notation varies; most commonly it's C7) is C, E, G, Bb. The dominant can also be added to the minor chord (forming a minor-minor seventh; Cm7), so that's C, Eb, G, Bb. The major seventh can also be added to either of these, forming the major-major seventh (CMaj7; the use of "maj" here is different from the triad) or the minor-major seventh (CMm7), C-Eb-G-B.

Lastly, the seventh, added to a diminished triad, forms a diminished chord. If you add the dominant/minor seventh, the chord becomes "half-diminished" (CØ7), C-Eb-Gb-Bb. The major seventh is typically not added to a diminished chord (though if you're after a very dissonant sound, this will certainly do the trick).

If you instead add the sixth (or the double-flatted seventh aka the "diminished seventh") to a diminished triad, the chord becomes "fully-diminished" (CO7), C-Eb-Gb-A. Mathematically, the fully-diminished chord is very important in music theory, because all of its notes have the same 1.5-step interval, and because there are only three unique combinations of notes that form a fully-diminished chord. C-Eb-Gb-A, Db(C#)-E-G-Bb(A#), and D-F-Ab(G#)-B. The next higher diminished chord, formed by Eb-Gb-A-C, has the same notes as the first; you may call it EbO7, but it's equivalent to the CO7 chord, it just has a different note on the bottom. It is, as we call it, an "inversion".

An inversion is usually notated the same as the normal triad, but instead of the root note being on the bottom, one of the other two are. The "first inversion" is formed by taking the root note and playing it an octave higher, so the third is "in the bass". The second inversion is formed by also playing the third an octave higher, so the fifth is in the bass. As I said, the notation usually doesn't change, however if it is important that a particular note be in the bass, it may be notated with a slash followed by the bass note: a first-inversion C major triad might be notated C/E, while the second inversion would be C/G.

Inversions and other "alternate voicings" are extremely common in music, especially pop music, for two reasons; first, because music in many forms is thought of as being formed by the movement of independent "voices" up and down by individual scale degrees, and second, because on many instruments, notably the guitar, it's difficult to play most chords with the root note "in the bass". You instead usually play the combination of notes however you can. In chords spanning multiple octaves, these defined inversions lose most of their meaning; you typically just start on the bass note (or any note in the chord you can sound) and play every note in the chord in every octave that you can until you're told by the sheet music to stop or you run out of strings or keys.

The sixth has become a more common addition to triads with the popularity of jazz. A C6 chord is a major chord with the sixth added on, often in an inversion with the sixth in the bass, where it forms a minor third under the root. Adding the second (also called the ninth) is also seen sometimes, especially in guitar music (a common way to form the C chord in the key of G will keep the D note from the previous chord; this is called a Cadd9 or a "country C").

Beyond this, most chord notation systems begin to break down, as representing "cluster" chords and others not based on a typical triad requires basically spelling it out.

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Super answer - just one point - Co ,as a diminished chord, should read C-Eb-Gb-Bbb.The note A would be a 6th, not found in a dim. chord. –  Tim Aug 16 '13 at 20:56
    
Umm, Bbb is A. The only reason to differentiate the two is that any key with a Gb would also have an Ab and so A is not part of the key (but a diminished 7th is never in the key of the diminished triad in the traditional modal scales) –  KeithS Aug 16 '13 at 21:50
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In this case, Bbb isn't A. It sounds the same, but will need to be written as a flattened Bb, thus Bbb.You're right in that Gb key has an Ab in it and that's one reason why the note can't be called A.The other is that as the note making the interval is already called Bb, when the interval is made smaller by a semitone, that Bb is flattened again. If, like me you're a guitarist, then we'll call it A, but we'll both be wrong !! –  Tim Aug 17 '13 at 11:21
    
I agree with Tim. A diminished 7th chord has a 7th in its spelling, because, well, it's a 7th chord. If you really want to confuse people, then call it a diminished 7th and put a 6th in there instead. Anyway, if you don't like the double flat, you can always call it a B# diminshed 7th and spell it B#-D#-F#-A. –  BobRodes Apr 17 at 19:59
    
B𝄫 sounds like A in equal temperament. It isn’t necessarily the same in just intonation or other tunings. –  Bradd Szonye Apr 18 at 20:46
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The notes in a chord determine the name of the chord.

The root note of the chord will start the name of the chord(eg. C) and then every chord type has it's formula which determines the notes in the chord. For eg. a Major chord has a formula of 1-3-5 so the notes in a C-Major chord are C,E and G. Similarly the formula for a minor chord is 1-b3-5 which means the notes in a C minor chord will be C,D# and G.

Here is a complete list of all the chord types and their formulae:-

http://www.smithfowler.org/music/Chord_Formulas.htm

I hope that helped

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When a flattened note is used, it cannot be called sharp, so the D# will have to be called Eb. It's the same sound, found in the same place, but in the written music has to be Eb. The 'Hendrix' chord actually has the D#, along with a Bb, and because of this, it's called C7#9 : C-E-G is C(maj.), Bb is dominant 7th, and D# is sharp 9th. –  Tim Aug 16 '13 at 8:25
    
Thanks for that...I get confused between the sharps and flats this way sometimes –  Rajeev Bhatia Aug 16 '13 at 8:46
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The root of the chord, plus a hint at which basic chord tones and tensions are included. There are basically five flavors of chords, so the chord names tend to reflect this fact:

Minor major dominant diminished minor-major

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From Howard Morgen's excellent course Fretboard Breakthrough at True Fire: The answer is Context. What does the chord precede or follow?

Chords separated from their context can be based either on choosing the lowest tone as the root, the third, the fifth or even seventh which could be inversions.

C E G = C Major triad or an Am7 first inversion? (w/o the root in this case)

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One simple way to notate 7th chords is to put the quality of the chord then the quality of the interval, then a 7. For example, a "dominant 7th" chord is a Mm7 chord; it has a major triad with a minor 7th on top of it. A "major 7th" chord is a MM7, a "diminished 7th" is a dd7, a "half diminished" is a dm7, an "augmented 7th" is aM7, and so on.

"How the common names are defined" varies from style to style. Your "sus 4" chord notation is very much a jazz convention; in Baroque music when they first became very common they were treated as a non-chord tone by later (say, after 1750) analysts. (Baroque composers didn't much think of "chords" at all; they were much more concerned with how the voices interacted as they moved, and did not think much at all about "harmony" per se. The rules they used were the rules of counterpoint, which spend much more time addressing "where to go from here" than "where we are now".

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