Sonata-form, Part 9: The augmented sixth

In the development section of a sonata-form, the end is often the dramatic focus of the entire movement— the place where a composer will attempt the musical equivalent of a quadruple Axel. In fact, at the end of my last installment, I left you with two of the most brilliant maneuvers in the literature: one from the Finale of Mozart's 41st ("Jupiter") Symphony, the other from the first movement of Beethoven's Fourth.

The last movement of the Mozart 41st is legendary for its power and complexity. It's Mozart's greatest homage to the work of J.S. Bach, whose music had suddenly changed Mozart from a boy to man six years earlier in 1782. It's therefore a deeply conservative work, a volcanic explosion of obsolete Baroque counterpoint completely out of step with the musical tastes of late 18th-Century Vienna.

The passage from the Beethoven Fourth is as forward-looking as the "Jupiter" Symphony's finale is retrospective. One of my pet peeves is the effect of Robert Schumann's remark about the Beethoven Fourth; he called it " a slender Greek maiden between two Norse gods." This unfortunate comment somehow gave rise to the ridiculous idea that Beethoven's even-numbered symphonies are lesser works than the odd-numbered ones. I'll resist the temptation to squander my allotted space debunking this misconception and content myself with observing that this particular example from the Fourth is one of weirdest experiments in all music history, as daring and unprecedented as anything from the 20th Century.

A sophisticated device

Despite their differences, the two passages both exploit the same underlying musical idea, one of the most sophisticated devices available in the toolkit of classical harmony. You don't have to read music to follow my explanation— just listen to the musical examples.

In the fourth installment of this series, I discussed the concept of being in a key— that is, the magical ability of the major scale to create the sense of a musical home base. As I said then, when certain notes from the scale"“ specifically, the fourth, fifth and seventh"“ are played together, their combined effect is to make you want to hear a tonic chord. In this combination— which is called, rather obscurely, a dominant seventh— the fifth note wants to move down to the tonic at the bottom of the scale; the seventh note wants to move up to the other end of the scale; and the fourth wants to move down to the third. In this example, the melody in the trumpet goes up the scale to the seventh note, the rest of the chord is filled in, and the resulting dominant seventh resolves to the tonic.

The tension isn't inevitable

Most development sections end by exploiting the expectation created by a dominant seventh; the development of the first movement of Beethoven's "Eroica" Symphony is, as we saw last time, the paradigm for this sort of tension. In fact, it's easy let yourself be convinced that there's something inevitable about the behavior of a dominant seventh— that in the classical style, a dominant seventh must resolve to the succeeding tonic. But if you listen to this example, you'll hear that it ain't necessarily so.

In this new version, every single note of the original dominant seventh chord behaves differently. The easiest difference to hear in this example is that the seventh note of the scale becomes a new tonic. In short, by changing the behavior of a dominant seventh in this way, we've modulated— that is, we've suddenly moved to a very distant key— one key whose scale has almost no shared notes with the scale we came from. In fact, the new tonic is the only surviving note from the original dominant seventh chord.

How it makes you feel

Since musical terminology names chords by their behavior— not simply by the notes that they contain— the chord we just called a dominant seventh is called by another name— an "augmented sixth"— when it behaves in this way. But don't worry about the terminology— just pay attention to what the music sounds like and how it makes you feel.

Here's the same situation reversed: an augmented sixth in, as it were, its natural habitat followed by the same chord as a dominant seventh. (Sounds a bit clunky going in that direction, doesn't it?)

You may rightly respond, upon hearing these examples, "Yeah, so what?" It took me many years to realize it, but there are many people who love classical music and respond to it deeply but simply don't care about the inner workings of classical harmony. In fact, I'm married to one of them. So as far as I'm concerned, "Yeah, so what?" is perfectly valid. But for me, hearing a dominant seventh become an augmented sixth is one of the miracles of the natural world, something akin to seeing a chameleon change color or a caterpillar turn into a butterfly.

How Mozart changed classical harmony

In the Mozart, the augmented sixth goes by in a flash; for me, it's sort of like that magical click when a combination lock opens. Beethoven, by contrast, uses the augmented sixth to distend musical time and space. So I'm not so deluded to think that, upon listening to the examples from the Mozart 41st and Beethoven's Fourth again, you'll say, "Oh, yes— they both use an augmented sixth to get back to the tonic. How silly of me not to hear that the first time."

But I do believe, perhaps quixotically, that after I've mastered the tools available to me with my snazzy new iMac computer, I'll be able to show you the details of how these passages work. And I certainly think it's worth the effort, because, as it turns out, Beethoven's fascination with this bidirectional chord led him to irrevocably alter the behavior of classical harmony and the basic underpinnings of sonata-form.

To read earlier articles in this series, begin here.
To read the next installment, click here.