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The dominant chord is defined in relation to the (5th) scale degree on which it is built. This definition can often be found alongside other chord types, such as the major triad, whose definition merely (I think) specifies its internal pitches ({0, 4, 7} in integer notation).

It seems to me one can talk of a major/minor chord just based on those internal pitch relations of its own constituent notes, without reference to the context in which it appears (e.g. the key), whereas to talk of a dominant chord requires (does it not?) a further specification of a key or cadence in which said chord functions as the V.

Is it, in fact, the case that indeed "dominant chord" presupposes a key (relative to which the given chord functions as V)? If so, why are dominant chords discussed in (apparent) isolation of a functional harmony, just as a chord type?

Or is it in fact the case that a key assumption is always (at least tacitly) present, even when one just talks of a plain major chord? If so, then the apparent paradox is that the dominant chord is of course (assuming it has no added seventh) itself a major chord.

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  • Too much double talk. Thin out the verbiage and the metacommentary a little, and get to the point. Your college professor is paid to read this stuff, Joe Schmoe on the internet is not. :D – Bennyboy1973 Apr 8 at 9:38
  • Based on the answers below, are we supposed to discuss dominant 7ths (and 9ths, etc.) or just dominant chords? Your last paragraph actually seems to imply the latter, yet all the answers currently address the former (possibly in addition to the latter). – Dekkadeci Apr 8 at 12:04
  • @Dekkadeci just dominant chords - I know dominant 7ths are popular, but my question was about local vs global roles for such a chord – z8080 Apr 8 at 14:42
  • @Bennyboy1973 alright, will try next time :-p – z8080 Apr 8 at 14:51
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I think the answer depends on both a) whether you mean a dominant triad, a dominant seventh, or both; and b) the style of the music in question.

If you mean a dominant triad only, then you're correct: by calling it a dominant, you are implying that this must be V, and therefore you're implying what tonic (I or i) must be.

But as Bennyboy mentions, the dominant seventh chord is so ubiquitous as a particular chord quality—a major triad with minor seventh—that is can be referenced as a chord quality without implying any particular tonic.

To clarify any confusion, plenty of musicians distinguish between a "dominant" and something that is "dominant quality." A dominant must be V, which implies a tonic; but something being dominant quality simply means that it is a dominant-seventh chord, not necessarily built on the fifth scale degree of a particular key.

This is especially clear in other styles of music. In Blues, for instance, you can have a dominant-seventh chord on IV. Obviously it's not functioning as a dominant, but the chord itself is a dominant quality.

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  • Thank you! I think I'm starting to get it, but as with Bennyboy's answer, I feel what still remains unclear (and what many might possibly prefer to just not have to put into words), is what gives the chord that quality, if not something that can be pointed to in the score. And I know the ii can function as a dominant, but I think you're getting at something broader here. – z8080 Apr 8 at 14:49
  • So Is it correct that V implies it needs to be some key's V, but a V7 can exist "in a vacuum"? – z8080 Apr 8 at 14:51
  • Oh, I think I see now. Are you asking how something can be made to sound like dominant without its tonic being involved? – Richard Apr 8 at 14:51
  • Any use of a Roman numeral implies a tonic, because the Roman numerals are always determined in relation to a particular I chord. In other words, calling something "V" means that you're relating that V to whatever is a fifth lower (tonic). But the chord quality of a dominant seventh can exist in a vacuum, yes; I'd just hesitate to use a Roman numeral if we're in a vacuum. – Richard Apr 8 at 14:52
  • But in that vacuum then, what gives the dom 7th its quality, other than being based on some tonic's 5th scale degree, and having an added m7? Don't mean to nitpick here, just to understand :) – z8080 Apr 8 at 14:54
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The dominant chord is so important as a key-defining chord that it's the only 7th chord referred to just like that: V7.

It also happens that (something like) the minor 7th is the next overtone in the harmonic series after octave, fifth, and major third. In other words, it works not only as a functional tone, but as an extension of harmonic texture.

So yes, the "dominant seventh" is built on the V of a key. But the chord type is so common and versatile as a textural feature, especially in blues or jazz, that when we say "dominant 7th," we are referring to the flavor of the chord, not its diatonic function.

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  • Thanks, that's very useful. I guess what I'm still unclear about is, what gives it that "flavor", other than the dissonance created by the m7? Is this local feature enough, or do we have to look at the context (e.g. the I that typically follows a V7)? – z8080 Apr 8 at 14:46
  • Timbre is the tonal quality of an instrument or sound, and it is based on the harmonic series (the sounds you will get if you divide a string into 2, 3, 4, 5, 6, 7 pieces. Depending on which of this sub-sections vibrate more or less, you will get a different sound quality. Take a guitar power chord. It is made up of tonic, 5th, octave, but those aren't treated as notes-- they are just part of that particular sound. – Bennyboy1973 Apr 8 at 21:44
  • Also, the m7 is a dissonance compared to the 5th or 3rd, but compared to most other notes, it is actually the next one to appear in the natural harmonics of an instrument-- so you can think of the 7th as "bringing out" a certain part of the natural harmonics to change the sound quality. – Bennyboy1973 Apr 8 at 21:46

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