In a discussion about blues music, a friend described the presence of both minor and major thirds in a dominant-seventh tonality as a blues innovation. I wondered if there were examples of dissonant non-chord tones in pre-20th century music that give this effect? The context that popped into my head was an augmented 6th chord (enharmonically equivalent to a dominant seventh) with a leading tone in the melody resolving to the tonic. The leading tone would function as the minor third, against the major third in the augmented 6th. But I couldn't think of any specific examples in pre-20th century music where this actually happens. Can anyone think of such an example?

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    The usual German augmented 6th (enharmonically equivalent to a dominant 7th harmony) contains scale degrees 6, 1, 3, and ♯4 of the minor key. It typically resolves to V, with the 6 and ♯4 expanding to the octave. It does not include scale degree (♯)7, the leading tone of the key. What do you mean by "the leading tone would function as the minor third"? – Remy Jan 27 '18 at 4:23
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    Agreed with Remy here, you’re notes don’t add up. Also, augmented 6th chords usually lead us somewhere, serving more as a pivot. It sounds like you and your friend were more discussing modal mixture. – jjmusicnotes Jan 27 '18 at 12:12

I think OP's question makes sense; they're asking about a minor third (well, an augmented second) above the bass note of the augmented sixth.

In C, an augmented sixth is A♭, C, and F♯. This is shown below in the "A" example.

enter image description here

But along with the C, I think OP is asking about also including a B, an augmented second ("minor third") above the bass A♭; this is shown above in the "B" example.

Now, regarding the actual question, I can't think of any examples that include both of these scale degrees.

However, while most augmented sixth chords function as pre-dominants, there are augmented sixths chords that function as dominants. One is shown below; note that the asterisked chord includes the augmented sixth from D♭ to B, and the chord is equivalent to a French augmented sixth chord. But note that this chord resolves to a tonic of C, not a dominant in F.

enter image description here

Whether or not this is a bona fide augmented sixth is up for discussion. Often it's just a V43 that then changes to a lowered scale-degree 2 before moving to tonic, but the point here is that this augmented sixth chord does include the leading tone. This is exactly how Bruckner used it in the Adagio of his Seventh Symphony, written in the early 1880s (I start the video at the overall progression, but the chord is at 4:20):

enter image description here

  • You're correct about my original intent - I was looking for something exactly like the 'B' example you described. Or really, anything with the same intervallic relationships - a chord with a minor third (or augmented second) above the root clashing against a major third, with a minor seventh (or augmented sixth) also. I see how your Bruckner example involves a leading tone in an augmented sixth chord, but it doesn't involve the "clashing thirds" that I am hoping to find. – Chad Jan 28 '18 at 4:50
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    I'm not sure how much luck you'll have looking for clashing thirds this early. But I'll keep thinking about it! – Richard Jan 28 '18 at 14:44

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