From what I understand, it is the 3rd scale degree along with the 1st and 5th scale degrees that are the most stable tones in a key so why in my textbook does it say that the 4th scale degree is used as an "anchor" tone (doubling note) when doubling 1st inversion triads in 4 part harmony? Wouldn't the 3rd scale degree make a better doubling note choice?

I am working from Kostka, Stefan M., Dorothy Payne, and Byron Almén. Tonal harmony, eighth edition.

  • 1
    Which triad is in first inversion when the fourth scale degree is doubled? In my experience one doesn't typically discuss scale degrees when discussing doubling, since the scale degree is always relative to the key, while doubling preference is relative to the root of the chord being voiced.
    – phoog
    Jul 6, 2021 at 17:12
  • 1
    It would be helpful if you would post the quotation from the book. That will give answerers the context of the question.
    – Aaron
    Jul 6, 2021 at 17:51

2 Answers 2


Walter Piston gives this same rule in Harmony. For first inversion chords double a tonal degree. The tonal degrees are ^1, ^4, and ^5.

The idea is doubling a tonal degree will reinforce the sense of tonality.

Let's make a table of the results for diatonic triads in C major...

I6    => C or G,     not E
ii6   => F, maybe D, not A
iii6  => G,          not E or B
IV6   => F or C,     not A
V6    => G, maybe D, not B
vi6   => C,          not A or E
viio6 => F, maybe D, not B

Consider the gamut of letters, they can be in an order, better to have them in a circle so we don't emphasize a starting point...

  A     G
  E     C
    B  F

...not a great looking circle, but just assume the letters are in no particular order.

Within that unordered gamut if you emphasized A and E, the tonality would lean toward A minor. If you emphasized C and G, the tonality would lean toward C major.

Notice that the list of letters to "not" double in C major are mostly A and E which are the modal degrees. Too much of A and E would lean to A minor rather than C major. Superficially you could have something like the bass and soprano melodically moving in what is clearly C major, but filling in full four voice harmony with too much modal tone doubling would conflict with C major by emphasizing the modal regions of A and E.

Think of it in terms of balance of tones. Emphasizing tonal degrees will emphasize the tonic, and the subdominant and dominant which support the tonic. You want the central role of the tonic loud and clear. Only a small amount of the modal degrees is needed to make clear the mode.

Piston, Harmony, 1st edition.

P. 13

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P. 87

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From what I understand, it is the 3rd scale degree along with the 1st and 5th scale degrees that are the most stable tones in a key ... Wouldn't the 3rd scale degree make a better doubling note choice?

When I think of stable versus tendency tones, I think of the tonic chord I and the resolution of V4/3 or IV6/4 to I to exemplify the resolution of non-tonic tones to tonic chord tones. Chord context matters. ^3 is stable by virtue of belonging to tonic I. Notice how ^4 differs depending on chord context. In V7 the ^4 is very unstable with tendency to resolve down to ^3 (as a stable degree in I.) But, in IV, the ^4 is the root and quite stable. In root position ^4 has no problem rising to ^5. So, when we talk about the instability of tendency tones there is at the very least an implied harmonic context.

In regard to doubling tones, I think we need to state the stability of ^3 in I simply does not define the tonality, in the sense of what is the tonic, but defines the mode. In other words, being a modal degree doesn't necessarily mean "unstable" tone.

We re-examine the Piston rule now. Let's say we have a V6/5, first inversion dominant seventh. The "rule" would say a tonal degree could be doubled. But, that would allow a doubling of ^4, which violates the fundamental "don't double a tendency tone" rule.

I suppose you could extend the rule to say "in first inversion double non-tendacy tonal degrees". I haven't tested whether that's a sound rule, but I think it is.

  • Thanks Michael. Interesting what you wrote but I was actually asking why the "tonal degrees" are 1,4 and 5 and not 1,3 and 5. The 3rd is more stable in the key than the 4th isnt it? So in C major, that E note is a stable tone and not a tendency tone like the 4th degree which resolves to the 3rd usually
    – user35708
    Jul 7, 2021 at 16:00
  • also, if we are doubling to reinforce tonality, why not double the 3rd instead of the root in the root position chords too... lets say the vi chord where it is the 3rd of the chord that is the central note of of the key (C in C major).
    – user35708
    Jul 7, 2021 at 16:25
  • @armani, I just added a bit more to my answer about stable/tendency versus tonal/modal degrees. I think it should answer the questions in your comments. Jul 7, 2021 at 16:53
  • @armani I'm going to add a short answer to explain where all of these rules come from. I think these answers describe the theory correctly but there is a bit of a disconnect between the theorists' reasoning and the actual reason for the rule.
    – phoog
    Jul 7, 2021 at 17:12
  • About root position vi, deceptive progression V vi would have ^1 doubled in vi. But that's more of a special voice leading issue. You probably want to examine that with some real examples. I imagine a lot of root position ii, iii, and vi could be explained as temporary tonic changes, or sequential harmony. Jul 7, 2021 at 17:34

One "rule" I heard some 70 years or so ago is that (in a major key), one normally doesn't double the third of a major chord (in any inversion) but one usually doubles the third of minor chords. This is equivalent to the original question.

The main reasons I have read (some years later) is that doubling the third of a major chord tends to make voice leading (avoiding parallels) difficult. Also a major chord with a doubled third sounds a bit like a Neapolitan Sixth.

  • 1
    The "rule" about doubled thirds generally comes from avoiding a doubled leading tone; that is, avoiding doubling a dissonance.
    – Aaron
    Jul 6, 2021 at 22:53
  • @Aaron while that is true, I have also found that doubled thirds are harder to tune (because thirds and sixths are more forgiving of imprecise tuning). Furthermore, the trouble is greater with major thirds than with minor thirds. Though I'm not sure that B in a G major chord counts as a dissonance, even if it's a V chord in C major.
    – phoog
    Jul 7, 2021 at 15:29

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