Musical Chords: What are majors, minors, 7s and 9s?

Factual Questions
1

I’ve got my guitar chord sheet out, trying to learn some chords, and I wanted to ask: What’s with all the chord variations? I mean, I understand that a B7 sounds a little different than a straight “B” chord, but what gives?

Why is one chord a major, the other a minor, one is a “B7” while the other is a “B9”? And what the heck is a “B7sus” and why is it called “sustained” (I think)? Is there any mathematical relationship between them all?

I’m an engineer, and may be looking at this a little too hard. Please tell me if I am.

Tripler
At this point, B. B. King I ain’t.

2

You are. It’s called a “B7” because in addition to the normal “B” chord (B-D#-F#), you’re adding the seventh note in the scale of B, i.e. the A natural. If it was a Bmajor7, you would be adding the A#. This is the same for any number after a chord; you’re just adding that particular interval.

A sustained chord is so called because it doesn’t feel “finished”, i.e. it sustains (or prolongs, I guess would be a better term) that feeling of getting to the tonic, or “finishing” note or chord. So your B7sus chord would consist of B-E-F#-A natural.

Hopefully this is what you were asking… I’m sure someone can explain the mathematics part of it better than I could.

3

You’ve asked a question that can only be answered with books and instruction, not a message board. This is Music Theory, and I suggest looking at Berklee’s website (I’m sure there are lots of others). Sorry, there’s no simple answer to your question.

One Link Of Many

4

Also, there’s 11ths and 13ths too…and Augmented, Diminished, minor7flat5 (;)) , etc.

5

Major chords are comprised of the 1,3,5 notes of a major scale. Minor chords are comprised of the 1,3,5 notes of a minor scale. The only difference with these 3 notes is the 3 note - in a minor scale and chord it is a semi-tone lower than the major scale or chord. e.g. C major is C, E, G and C minor is C, Eb, G.

(at this point, you are saying “Great, can’t learn chords until I learn scales”.)

The 7, 9, 11, 13 etc. are adding those scale notes. E.g. C9 has a D in it. (yes, could have called the D the 2 note of the scale, and the chord, but it isn’t usually done that way.) Another peculiarity, the 7 is really the flattened 7. E.g. C7 is C, E, G, Bb. C Major 7 is C, E, G, B (see DooWahDiddy’s example too)

C minor 9 is C, Eb, G, D

btw, when you have a ninth chord, it includes the 7 (flattened 7th that is). When you have an 11th chord, it includes the 9 and 7 (flattened). If you wanted C, E, G and D, but no Bb, it is usually written C add 9.

The “Suspended” business is adding the 4th (aka 11). I think the terminology comes from ancient harmony, whereby they had a hard time accepting dissonances, so they always got the 4th note from the previous chord. See link

6

Before worrying about 7’s and 9’s and whatnot, consider simple triads. This is probably easier understood with a piano than a guitar.

Triads, as you would suspect, have three notes. A major triad consists of the intervals of a major-third and then a minor-third. For example, the C-major triad is the notes C, E and G. From C to E is a major third, or four semitones. The notes C#, D and D# are in between. From E to G is a minor third, or three semitones. The notes F and F# are in between. (On a piano keyboard, you will notice that there is no black key between E and F. Thus the difference between E and F is a semitone, the same difference as between C and C#.) The interval from the root (or tonic), C, to the highest note, G, is a perfect fifth, or seven semitones.

C-major is called “major” because it sounds full, happy and complete. The notes also come directly from the C-major scale, C, D, E, F, G, A, B, C.

A minor triad is a major triad upside-down. It consists of a minor-third and then a major-third. The interval from the tonic to the highest note is still a perfect fifth. Thus, C-minor must have C and G. Moving the middle note down one semitone to E-flat gives us a minor third followed by a major third. A minor triad is minor because it sounds hollow or sad and somewhat dissonent. Notice also that the notes of a C-minor triad are taken directly from the C-minor scale, C, D, E-flat, F, G, A-flat, B-flat, C.

You may be wondering why these intervals seem not to be directly related to the number of semitones between things. Why does a perfect fifth have seven semitones, for example? The reason is because our modern tuning system with 12 notes per-octave is a compromise based on historical tuning systems which are a fascinating subject in their own right. But note that when we consider the subsets of eight-note major and minor scales, a fifth is formed by the first and fifth notes of the scale, not counting the notes outside the scale.

Similarly, a triad is always formed by the first, third and fifth notes in a scale. The first, third and fifth notes of a major scale give you a major triad and the same notes from a minor scale give you a minor triad.

Remember how both kinds of triads have a perfect fifth in them? What happens if we mess with that? Say we take C-major (C-E-G) and change it to C-E-G#. Now we have two major thirds. C to G# is an augmented fifth. This is a C-aug triad. Now say we mess with C-minor (C-Eflat-G) and change the G to G-flat. Now we have two minor thirds. This is a diminished triad, and the interval from C to G-flat is a diminished fifth.

So now you know all about triads. More complicated chords are constructed by adding notes to these four basic forms. (Usually.) A seventh chord adds the seventh note from the scale of the triad you started with. The notes for C-major come from the C-major scale, so C7 consists of C, E, G and B. The interval from C to B is a major seventh.

A suspended chord usually has the third replaced by a fourth. For example, C-major suspended would be C-F-G. A Csus7 would be C-F-G-B.

B9 is left as an exercise for the reader.

If you’re an engineer you will appreciate the mathematical relationships between scales, chords and tuning systems. But the topic is vast and requires lots of reading.

Here are some good books:

Tonal Harmony by Stefan Kostka and Dorothy Payne
Temperament: How Music Became a Battleground for the Great Minds of Western Civilization by Stuard Isacoff (This is a must-read for anyone who wonders where our seemingly arbitrary 12-note chromatic scale came from.)

7

Nitpick: A Csus7 would be C-F-G-Bflat. C-F-G-B would be Cmaj7sus4

Another nitpick (which is important, because Tripler may be scratching his head going, “but A isn’t the 7th note of the B major scale.”) A# is the 7th chord of the B-major scale, not A. I really don’t want to delve too much into harmony theory, but a plain 7 after a chord (as opposed to maj7) always indicates dominant seventh. The dominant seventh is a whole step below the first note of your scale (or, more accurately, five whole steps above). Therefore the 7 in C7 refers to the addition of the B-flat, a note that does not appear in the C major scale.

A suspended chord is so-called because of its unresolved nature. Play a C-F-G on the piano, and you can hear that F wanting to resolve to either E or E-flat. Suspended chords come in two varieties, the suspended 4th (as in the previous example. It is the most common form of suspended chord, and is your default sus chord), and the suspended 2nd. In C, the chord would be C-D-G. Suspended chords NEVER include the 3rd. The suspended 2nd or 4th takes the place of the third in these chords.

8

Ugh, that should read:

"A# is the 7th note of the B-major scale, not A.

9

Good point. It’s been a long time since I studied all this stuff.

10

You’re right; I should have been more specific. I’ve been doing it for so long without thinking about it (playing piano, that is) that… I forgot. Or something. Oh and plus it’s 2 in the morning. :slight_smile:

11

OK. I’m going to try to give you a quick primer on the basics of harmony.

Chords, by definition, must contain 3 notes or more. 2 note chords are technically called intervals, not chords.

In standard tertiary harmony, a chord has three notes:

root-third-fifth

Here are all the flavors of chords you can derive from these three notes, and let’s use the key of C as our example.

root-Major 3rd-fifth (C-E-G) Major chord
root-Minor 3rd-fifth (C-Eflat-G) Minor chord
root-Minor 3rd-flatted fifth (C-Eflat-G-flat) Diminished chord
root-Major 3rd-augmented fifth (C-E-G sharp) Augmented chord

So, when you hear a chord, these are the four basic “flavors” you’ll be looking for. Almost all chords (excepting suspended chords which replace the 3rd with a fourth or second) are based on these four chord types.

After the third, the most important note in Western harmony is the seventh. The seventh comes in several varieties: the dominant seventh, the major seventh, and the diminished seventh. The dominant seventh is 5 whole steps up from your root. The major seventh is 5 1/2 steps up, and the diminished 7th is 4 1/2 steps up. The diminished 7th is only used in diminished chords.

So, taking our example from above

Major chord plus dominant 7th = (dominant) Seventh Chord (e.g. C-E-G-Bflat is a C7)
Major chord plus major 7th = Major Seventh Chord (e.g. C-E-G-B spells Cmaj7)
Minor chord plus dominant 7th = Minor Seventh Chord (e.g. C-Eflat-G-Bflat spells Cm7)
Minor chord plus major 7th = Minor Major Seventh Chord (e.g. C-Eflat-G-Bnatural spells Cmmaj7 or Cminmaj7)

These two are much less common, but for sake of completion:

Augmented chord plus dominant 7th = Augmented Seventh Chord (e.g. C-E-Gsharp-B-flat spells Caug7, or C+7, or C7#5)
Augmented chord plus major 7th = Augmented Major Seventh Chord (e.g. C-E-Gsharp-B spells Cmaj7#5–this is not a common chord, and therefore doesn’t really have any standard notation, but this is most commonly how you will see it written out.)

The third and the seventh are the most important notes of basic Western harmony. Notes beyond these (the 9ths, 11ths, 13ths, sixths, etc) are generally just there for color. The fifth, unless it’s augmented or diminished, can almost always be gotten rid of.

12

By “you,” I am referring to Tripler, of course, not DooWahDitty and friedo, who obviously know their stuff, lest there be any confusion since their posts weren’t there when I was composing my reply.

13

Oh, since I’m being pedantic, that should really say, “a chord begins with three basic notes.”

And it doesn’t HAVE to have a third, it could be a suspended fourth or second; but that suspended fourth or second will want to resolve to either the major or minor third depending on context.

14

I’d recommend this site to be able to hear some of what’s being described here.

Heh heh, nitpick time…a two-note chord obviously isn’t a triad, but is surely no less of a chord? What about the open-fifths endings of plenty of medieval music, do they not end on chords? I’ve rarely come across a ‘3-note-minimum’ definition. And an interval is a theoretical construct to describe what’s happening, but isn’t the notes itself. (Am I being awkward enough? :wink: )

15

Ack, well I suppose my medieval example is ruled out by your subsequent post which I failed to pay proper attention to…but I stand by my general comment :slight_smile:

16

Interestingly, my dictionary says a chord is “three or more musical tones played simultaneously,” but my theory instructor always insisted the proper definition was “two or more intervals played simultaneously.”

I never could figure out what the difference was.

17

If simply learning how to play is what your after then I would suggest you not get bogged down in the specifics of why things are the way they are, just accept it. Many people are quite adept musicians without knowing the theory behind it in the same way that many people can speak quite beautifully without knowing parts of speech.

18

I think he was describing the same thing in a different manner.

Intervals are two tones, chords three or more. It is possible to say that the interval of C,E played simultaneously with E,G is a chord (two intervals played simultaneously), but it is pretty pedantic to do so.

An interesting exercise I often use to illustrate the importance of the 3rd in a triad is to loudly play all C’s and G’s on a keyboard, then ask, “does this sound major or minor?” The answer should be, “neither,” since the defining note is not present. Then I play the same thing again, followed – before the sound dies out – with a very soft, single E somewhere in the middle of the keyboard. This single E is sufficient to make our ears hear “major”. Then do it again with a single E-flat – sounds “minor”. You can do this same demonstration with only the C (omitting the G) to show how unimportant the 5th is to a triad.

19

But aren’t there technically only a few different families of chords? Where would a two note chord fit in?

I’ve also seen it referred to that the ninthis the second of a scale but raised an octave. Indeed, I’ve seen Cadd9 referred to as Cadd2 if the “ninth” is in the same octave. Same with eleventh and thirteenth. Is this correct?

You might like to read the book “Chord Chemistry” by Ted Greene. I don’t know whether it’s still in print, however, but it certainly helped me to understand what was going on. You can also read the theory articles over at www.cyberfret.com but they’re not as in depth as CC.

20

There’s far more than a ‘few families’. There’s an practically-endless number of different chords within the chromatic system. The most common ones, those which take particular functional roles in western music, have been assigned names - including two-note chords, called dyads.