Musicians use the word “seventh” to mean two different things.
When it’s a full major (or minor) chord, played with its root on the seventh note relative to the tonic (the root of the key of the whole song), that “seven” chord is based on the TWELFTH half-step of the octave. For example, if a song is in C, the VII chord is a B chord. That’s why you have to call a B-flat chord in a C song a “FLATTED seventh” – because it’s the 11th half-step, not the 12th.
However, when you use the word “seventh” to mean simply adding an extra note to a chord, making it “demand” resolution (or just making it sound bluesy), the word “seventh” refers to the ELEVENTH half-step of the chord, not the 12th; for example, adding a B-flat to a C chord. That’s why, if you add a B note to a C chord instead, you have to call it a “*major *seventh”, not just a plain “seventh”.
Why is the word “seventh” used to mean different intervals, depending on if one is referring to a whole new chord vs. just adding color to an existing chord?
You are mixing up two different things. The numbering system for relative chord positions (in C , II is Dm, III is Em, IV is F…) the five/V chord is G7 - the dominant seventh. The seven/VII chord is Bm. As Zeldar’s link says Jazzers tend to include the sevenths for all positions (I to VII) other styles of music will typically only routinely include the seventh note in the dominant chord.
You’d use the term “flattend seventh” to refer to a “dominant” seventh shape played as something other than the five/V chord. There’s a bunch of Beatles songs that have a flattend seventh as the home chord, IIRC You Can’t do That is a good example.
If a song in the key of C contains a B-flat chord it’s probably best described as a borrowed chord. Bb doesn’t belong in C it’s probably functioning as the IV chord in a modulation to F, or something. If you’re playing rock though, anything goes.
They’re both sevenths. One is a major seventh, and one is a minor seventh. The most common kind of seventh chord contains the minor seventh, so “seventh chord” is taken to mean this. A chord that contained the major seventh instead would be explicitly called a “major seventh chord”.
Red color mine. In the one case, it’s a SEVEN (not SEVENTH) chord, in the context of identifying to the chord in reference to the major scale of the key one is in. In the key of C, a C chord is a I chord, an F chord is a IV chord, a Bb chord is a bVII chord, a B chord is a VII chord. Note that a IV chord may be a IV (F), IV7 (F7), IVm (F minor), etc.
In the other case, it’s naming the chord with reference to the individual notes that comprise the chord in reference to the major scale of the chord’s root. Thus a C chord is understood to have notes 1, 3, & 5 of the C major scale (c, e, & g), regardless of what key one is playing in. [If one is playing in C, the C chord is a I; if playing in F, it’s a IV; if playing in D, it’s a bVII; etc.; but in whatever key it’s a C.] A C7 is understood to have notes 1, 3, 5, & b7 (c, e, g, & bflat). In the nomenclature, an X7 is BY DEFINITION UNDERSTOOD to contain the FLATTED 7th note of the X major scale. Thus, if one wants a chord with notes 1, 3, 5, & 7, it is called an Xmaj7, to distinguish it from the much more common X7.
Not every 7th chord is automatically a dominant 7th. Dominant refers to the fifth note of the major scale, so in a given key only the V7 is the dominant 7th. In the key of C, a G7 is a dominant 7th, but in any other key G7 is simply G7.
ETA: To clarify a bit, and probably get to the root of your question – an X7 chord is very common and thus over time, even though it uses a b7, it got to lay claim to “7.” The major seventh chord, while it uses the actual 7 rather than b7, came late to the party and had to settle for “maj7.” It’s just a matter of how things evolved in using and naming chords.
At the risk of starting a flap: X7 is NOT a dominant 7th chord UNLESS X is the fifth note of the major scale of the KEY of the song in question. Yes, all over the internet you can find sources that call an X7 a dominant 7th irrespective of the key. They’re wrong.
This is based on the word names for the notes of a major scale, as shown here (see “degree”). In the key of C, a C7 is a tonic 7th, a D7 is a supertonic 7th, etc. – only the G7 is a dominant 7th when playing in the key of C. And G7 is a dominant 7th only when playing in the key of C.
The chord built on the seventh degree of a major scale is not a minor chord, but a diminished chord. It is notated as the vii[sup]o[/sup] and, in your example, would be B diminished (B-D-F).
The VII chord of a major scale is the half-diminished seventh chord, also called the minor 7 flat 5. In the key of C this is Bm7b5 with the notes B D F A.
The 7th interval may be minor or major, but nothing else. There is no such thing as a “dominant 7th” interval. “Dominant 7th” refers to the entire chord. The dominant is the fifth step of the scale. Therefore the 7th chord built on the fifth step of the scale is the “dominant 7th” chord. In the key of C, the dominant 7th is G7 with the notes G B D F.
Chords in a major key are simply stacked up on each note using the scale. Here are the chords in the key of C with their scale degree names, chord tones, and chord names:
C tonic C E G A Cmaj7
D supertonic D F A C Dm7
E mediant E G B D Em7
F subdominant F A C E Fmaj7
G dominant G B D F G7
A submediant A C E G Am7
B leading tone B D F A Bm7b5 (or B half-diminished 7th)
The maj7 is a “major seventh” chord, major triad with major 7th
The m7 is a “minor seventh” chord, minor triad with a minor 7th
The 7 is a “seventh” chord or “dominant seventh” chord, major triad with minor 7th
ETA: The VII chord is built on the diminished triad so I agree with pulykamell’s post on that. My info above takes into account the 7th as well.
That might be true in the strictest classical harmony sense, but it’s not true as musicians world 'round use that phrase, at least in jazz/rock/blues harmony.
Yes, I know I’m fighting an uphill battle, and I don’t expect that common usage will change. I’ll just throw this out as food for thought:
What is there being called a dominant 7th is EXACTLY the same as a 7th chord (i.e., X7 = X dominant 7th). There’s nothing gained in terms of information or clarity by calling it a dominant 7th. And no, it doesn’t (or shouldn’t) distinguish it from a major 7th chord which has its own distinct name.
It is useful, however, to have a special name for the V7 chord because of its function within a given key. Given that the 5 tone of the scale is called the dominant, the term dominant 7th fulfills this role. To call a I7 or II7 (etc.) a dominant 7th muddies this.
Okay, I’ve had my say. If the other 97% of the world would like to join the crusade, hop aboard.
I think it’s useful to have a modifier when you want to distinguish this particular 7th chord from 7th chords as a class. Like, say, you want to say something like “Blues harmony is heavily based on dominant seventh chords–major seventh chords are rare in this context.” I mean, I suppose you can say “plain seventh chords” or “seventh chords with a minor seventh” or something like that, but “dominant seventh” works fine.
Usually, yeah, when naming chords the “dominant” modifier is left off, because it’s not necessary for context. You’d say “D7-G7-C” not “D (secondary) dominant 7th, G dominant 7th, C.” But if some tone-deaf musician had to ask, “Hey, Bob, what kind of seventh chord is that D?” I think the cleanest answer is a “dominant seventh.” (And, actually, it is strictly a dominant, although a secondary dominant, being the V7 of V. But I don’t want to expend that many brain cells for simply naming the character of a chord.)
I guess I’m coming from a different perspective, where a major 7th is always called a “major 7th” chord, and my answer would be “Did I say MAJOR 7th? No? Then it’s a 7th, or I would have SAID major 7th.”
Seriously, I have never heard the term “7th” used to refer to a major 7th. In my world, “7th” means only 1-3-5-b7, and “major 7th” means 1-3-5-7, the terms are consistently applied, and there’s no confusion. I’m guessing this is probably because I have less experience playing in bands and such as you do.
Disagree:
The interval from C to B is a major seventh, the interval from C to Bb is a minor seventh, and the inteval from C to Bbb(A) is a diminished seventh. A minor seventh chord has a minor third interval (C-Eb), a dominant 7th chord has a minor seventh interval (C-Bb).
It’s also the interval between the third and the seventh that makes a chord dominant, not the interval between the root and the seventh.
Thank you all…consider the main question answered, though there are some disputes over details.
Quite true…John Lennon played a role in starting the trend of using this “borrowed” chord in rock music, with 1966’s She Said She Said…then, in 1968, for some reason, British rock groups, especially, starting using it a lot (coda of Beatles’ Hey Jude, the Stones’* Sympathy for the Devil *and Stray Cat Blues, etc.).
As Alan Pollack puts it, it really belongs to a modal tradition, and has no place, really, in post-Renaissance Western tradition. But in these and other rock songs, it’s used as a kind of weak, wistful alternative to the usual dominant (V chord)…in all the examples I gave, the next chord is the normal subdominant (IV chord).
(So, if the song’s in C, as a transition to F, as Small Clanger put it…but not really as a full-out, key-changing modulation, but just as a repetitive chord sequence, still “in” the key of C.)
