Dominant seventh vs Dominant function [duplicate]

I saw how in the major scale the diatonic functions are:

I - tonic
IV - subdominant
V - dominant

and the V7 is called a dominant seventh

Also in the natural minor scale the diatonic functions are:

i - tonic
iv - subdominant
v - dominant

and I thought the v7 would be called dominant seven, but the v7 is a minor seventh. and the dominant seventh chord is actually the vii chord degree in the natural minor scale.

Which leads me to my question, are the dominant seventh and the dominant function two different things? So the dominant seventh chord is just another name for a major-minor-seventh chord. And that is completely different from a dominant diatonic function? Meaning the word "dominant" is not the same in these two contexts.

8 Answers

If you want a strong dominant function in a minor key, use V (or V7) not v. That's why the Harmonic Minor scale exists, because even in a minor mode we still sometimes want to write functional harmony.

Yes, we often call a major triad with a minor 7th a 'dominant 7th', referring to the chord shape rather than it's actual function. Very often a 'dominant 7th' type chord will have a dominant function. Not always. Prime example being the Blues. I7, IV7, V7. All 'dominant 7th' shape chords. Not all acting as dominants of something.

I think you've got this basically right. People often call chords like C7 dominant seventh chords to distinguish them from major seventh chords, regardless of how the chord is actually functioning. In a blues, you might have I7, IV7, and V7 chords, which are all dominant seventh chords, but not all dominant-functioning.

I suppose you could call dominant seventh chords major-minor seventh chords, as you suggest, but these could easily get confused with minor-major seventh chords. Probably better to stick with conventional usage here.

The naming of the notes isn't always consistent. The major scale is fairly easy. There are seven (different) diatonic notes; the other five tones from the chromatic scale are called "chromatic" to distinguish them from diatonic notes. There are actually 21 named notes (each note, its sharp, and its flat) for a total of 12 different notes.

In the minor mode, things are not as well described. There are still seven note names, but.....there are two "mutable" notes. The "natural" form of the minor scale has seven notes but compared to the major scale, notes 3, 6, and 7 are a half step lower. To get a half step close from note 7, the 7th note can be raised (gives a major V chord too); then to avoid (for singers) the augmented 2nd between note 6 and raised note 7, note 6 is raised. Neither of these moves is treated as chromatic in general.

If one keeps seven note name and writes out the 4 different scales that occur when sorting the notes by pitch, one gets four forms of minor scale. The "natural" minor is just 1,2,3,4,5,6,7; the "harmonic" minor is 1,2,3,4,5,6,#7; the "melodic minor" is 1,2,3,4,5,#6,#7 ascending and 1,2,3,4,5,6,7 descending. There doesn't seem to be a common name for 1,2,3,4,5,#6,7 but that doesn't mean there are not occurrences of this pattern.

From a Common Practice Period harmonic point of view ("classical harmonic") there are only two modes: the major and the minor (which has mutable notes.) In classical theory, scales are just the result of sorting notes by pitch so the minor mode is usually thought of as the "natural" minor scale with two mutable notes rather than three separate entities. There are lots of classical pieces with all three forms of scale occurring the same passage. I don't know enough about jazz and popular harmonic descriptions to go into to discuss much of their usage.

There are a few tendencies used in classical music related to mutable notes; these are only tendencies and other practices are not uncommon.

When the underlying harmony of a passage is tonic, tones 6 and 7 are often raised in ascending passages and lowered in descending passages. This gives rise to the "melodic" minor. However, often the 6 is kept lowered and the7 raised in instrumental music.

When the underlying harmony is subdominant, the "natural" form is used for both ascending and descending scale passages (the lowered 6 is the third of the iv chord.) Again this rule is sometime broken.

When the underlying harmony is dominant, the raised form is often used in both ascending and descending passages. Again the "harmonic" minor occurs too. The flat 7 forms a ninth chord with dominant harmony.

The arpeggio on a dominant chord is common which leads to the raised second between the lowered 6 and raised 7 steps. (2,4,5,b6,7 is a dominant ninth in third inversion.)

If you merely look at the notes in a chord without considering its musical function, then a "dominant seventh" is identical to a "major-minor seventh".

But that misses the point of the name, which shows that the dominant seventh chord has a strong tendency to resolve onto a chord which functions as a tonic chord - the third of the dominant seventh resolves up a semitone, and the seventh down a semitone.

IF the "dominant seventh" chord really is on the dominant of the scale, that means it resolves onto the tonic chord (in C, the B and F in the G7 chord move to C and E in a C chord).

There are several forms of the "minor scale" and the harmonic function of the dominant (or dominant 7th) chord implies that the leading note of the scale is a semitone below the tonic, not a whole tone as in the (descending) melodic minor scale, or the Aeolian mode.

Keeping in mind that every scale really contains all 12 chromatic notes, "dominant 7th" chords can be formed on any note of the scale, and they often resolve harmonically as if they were the "real" dominant 7th of a different key. Such chords are described as "secondary dominants". A good example is the start of Mendelssohn's well known "wedding march", where the harmonies (in key C) start C B7 Em F G G7 C. The B7 chord (including D# and F#) is still in the key of C.

150 years ago this C B7 Em ... chord sequence might have been described as a "passing modulation to E minor" but that description is not musically very enlightening - if you delete the B7 chord, nobody would think of describing the chord sequence C Em F G G7 C as "modulating" from C major to any other key.

An example in popular music is Abba's "Waterloo", which starts (again in C major) C D7 G ... where the D7 chord (with an F#) is still in C major and is the "secondary dominant" of the following G chord.

• It might be in C major, but it's not diatonic. The description 'in C major' isn't too definitive. Also, not sure I agree with the statement every scale really contains all 12 chromatic notes. A chromatic scale does, but a simple major or minor, or even blues scale doesn't. That's not to say all 12 notes can't be used in a piece in one key, but that's not the same. – Tim Aug 12 '18 at 9:08

Quote: "Which leads me to my question, are the dominant seventh and the dominant function of two different things? So the dominant seventh chord is just another name for a major-minor-seventh chord."

You are partially right. I think the confusion comes when you look at chord naming conventions and harmonic functions. These are different things.

1) Naming: for G major, (numbers represent the notes)

1 3 5 7 - G major7,

1 3 5 b7 - G7,

1, b3,5, b7 G minor7 ( b7 is G# !)

2) Harmonising

Most Music ends with V-I strong cadence. Putting aside the theory we like this. It's difficult to imagine a classical music piece without ending with a spiced up V-I.

Here comes that confuses you I think: C major V-I is Gmajor (or G7) to Cmajor. Sounds good. CM-s parallel natural minor scale Am. b7 here is g# that is outside the natural minor scale and secondly is a minor key so it just doesn't serve as a strong cadence that resolves to C. TRY IT! ( put aside the theory, try Gm-CM - doesn't sound too good). The solution is ( first done of course i classical music hundreds of year ago, to simply play G major chord instead of Gm: GM-CM TRY IT it sounds convincing. G7 is a major type of chord ( b3 minor type 3 major type scale/chord). So even if you play A minor blues you can use G7.

Your ear always proves if something in theory right or wrong if it sounds good is good is it sounds bad is bad.

I tried to be simple as possible so this is not a full music theory explanation, but I hope your question is answered.

• CM's relative natural minor scale Am. Parallels start on the same root note. And - b7 here is G. The 5th para. appears a little mixed up. – Tim Aug 12 '18 at 9:11

Actually, as I feel, it is dominant's (G on C major scale) seventh (F) which is correctly a flat seventh of Basic major scale of that dominant note G, and aesthetically that flat seventh degree implanted to basic major scale. So actually it is dominant's seventh and not dominant seventh. And the other 7th involves perfect 7th, hence called major 7th.

Not sure your penultimate paragraph rings true. Also, you seem unaware that there exist more minor scale notes than those found in the relative minor. There are also melodic and harmonic minors, both of which contain notes which make proper dominant sevenths, with that all-important major third note, found as the raised seventh note in each scale. As in D minor, with its C#, thus producing a dominant seventh chord comprising A, C#, E, G.

There are some contexts where the phrase "dominant seventh" is used with a purely functional meaning, to refer strictly to a seventh chord serving dominant function, e.g., a V7 leading to a tonic:

the demand of the V7 for resolution is, to our ears, almost inescapably compelling. The dominant seventh is, in fact, the central propulsive force in our music; it is unambiguous and unequivocal.

(emphasis mine)*

That said, I don't think this usage is at all the norm in most contexts. Certainly all over this website and in the vast majority of guitar books, the phrase "dominant seventh" generally seems to mean to mean "major-minor seventh"; even if someone wanted to argue this usage is strictly incorrect, it is at the very least informal popular usage that you must be prepared to understand as such.

I'll admit I try to err or on the side of caution and use "major-minor", but it doesn't roll off the tongue anywhere near as well as "dominant". I guess the short answer to your question is "common usage is slightly inconsistent, but unless implied by context, you can generally understand the phrase to refer to any major-minor seventh chord".

* Goldman, Richard Franco (1965), Harmony in Western Music (London: Barrie and Rockliff), pp. 34–35. ISBN 978-0-214-66680-3; lmao I'm actually just trusting Wikipedia sourced this quote correctly