Why.....

[TBman]

does a C7 chord have a flatted 7th, (b), but a E7 chord does not have a flatted 7th? (D)

[mr. beaumont]

Flat in terms of the major scale based on the root of the chord.

[JonPR]

Is this a test question for readers? Or are you really curious?

The answer is the 7th is "flat" only in relation to the major scale of the root. I.e., it's flat in the sense of "lower", not in the sense of requiring a flat accidental.

The 7th interval is "minor" in each case (i.e., a half-step lower than a "major 7th"). Both chords have a major 3rd and a minor 7th, which is what marks out a "dominant 7th" chord - because the word "dominant" means "5th step of scale" (V), and that' the only scale step (in major and harmonic minor) where you get such a chord diatonically.

I.e., C7 comes from F major (or F harmonic minor), while E7 comes from A major (or A harmonic minor).

But of course the chords are built the same way regardless of what key we use them in. So "major minor 7th" is the best way to think of the structure, not "major flat 7th".

Also...

"Major" and "minor" originally just mean "bigger" and "smaller" (Latin), and refer to all the intervals which come in two sizes: 2nds, 3rds, 6ths and 7ths. Chords and scales are named - firstly - after their 3rds. So a "major scale" is one with a major 3rd. The other intervals happen to be major or perfect too, but in minor scales, the 2nd is always major and the 6th and 7th can be either minor or major; only the 3rd is always minor.

When 7ths get added to chords, the most common one is the minor 7th, and we also assume the 3rd is major (unless marked "m"). Which is why "C7" doesn't need to say what kind of 3rd and 7th it has. But "Cm(maj7)" tells us both have been altered: to the "lower" 3rd and the "higher" 7th.

[hubcapsc]

The seven of E is D-sharp, so D is indeed a flatted 7th...

-Mike

[TBman]

Originally Posted by hubcapsc

The seven of E is D-sharp, so D is indeed a flatted 7th...

-Mike

So it's based on the intervals, not the note scale.

[mr. beaumont]

Interval, yes...not sure what you mean by note scale...

I'm going to start a topic about chord formulas. I hope it helps.

[Chipotle]

Originally Posted by mr. beaumont

Flat in terms of the major scale based on the root of the chord.

This. A chord is a series of tones from the scale. Each chord name has formula for a particular set of tones*. Flatted (or sharped) is just a half-step difference from whatever that tone was supposed to be based on that scale.

Major formula: 1-3-5. Minor: 1-b3-5. Seventh: 1-3-5-b7

C scale is C, D, E, F, G, A, B, so 1-3-5 is C-E-G, and 1-3-5-b7 is C-G-G-Bb.

E scale is E, F#, G#, A, B, C# D#, so E7 is E-G#-B-D... so it *is* flatted, or down a half-step, compared to the "normal" 7th note of the scale.

* You can express this formula in terms of the scale tones, or in terms of intervals from the root note; they are equivalent.

[TBman]

I'm forgetting the sharps and flats of the scales, that's where I blundered. Ok, thanks everyone.

[Charlie Bernstein]

They do. The C7's Bb is a flatted B, and the E7's D is a flatted D#.

[The Bard Rocks]

Keep in mind, there's no B#.

[TBman]

Originally Posted by The Bard Rocks

Keep in mind, there's no B#.

Wait... what?





What I did wrong was I laid out a few scales in Excel using the note names, but I forgot to put the notes as sharp as appropriate (for the D scale, E scale, etc). So obviously as my old BASIC programmer instructor used to say, "Garbage in, garbage out."

[JonPR]

Originally Posted by The Bard Rocks

Keep in mind, there's no B#.

Yes there is.
It's what we call "C" whenever were in the key of C# (major or minor), because B# is the major 7th scale degree. When we play a G# major chord (V of C# or C#m), it's 3rd is B#, not C.
Obviously it sounds the same and is played the same, but it needs a different name so that (a) each note in the scale has its own line and space in notation, and (b) the theory makes sense. The "3rd" of a chord is the 3rd letter up the scale from the "1st". If the 1st is a G of some kind, then the 3rd must be a B of some kind. It's Bb on a G minor chord, and B on a G major chord. So it's B on a G#m chord and B# on a G# major.

For similar reasons there is also an E# (7th in F# major, 3rd of a C# chord), a Cb (root of the Cb major scale, 4th of the Gb major scale, 3rd of an Abm chord, 7th of a Db7, and so on), and an Fb (there is no Fb major scale, but Fb is 4th of the Cb major scale, 7th of a Gb7, 3rd of a Dbm... )

Of course, if you don't read music, and don't care about theory, none of this matters at all!

[Silly Moustache]

Originally Posted by TBman

does a C7 chord have a flatted 7th, (b), but a E7 chord does not have a flatted 7th? (D)

Barry, the flat 7 of C is Bb not B.