A-flat Major P&F

I was surprised at how much I enjoyed learning these two. I always considered this set pretty “middle of the road” — enjoyable to listen to, but not one of my favorites. When I first began learning them, my initial reaction was that both the prelude and the fugue were kind of long, and have passages that were going to be a pain to decipher. But as I got to know them better, these two became some of my favorites, full of surprising amounts of dramaticism and virtuosity. 

The Prelude

To be honest, this prelude still kind of confuses me. On the one hand, there are passages that point to a toccata-like style and texture. On the other hand, there are passages that are quite lyrical. The prelude opens in an improvisatory fashion — A-flat major chords in the right hand; the left hand arpeggiating the same harmony over the first measure. Then, the right hand introduces a new, solo line that moves through one of the most basic transitions, from tonic to subdominant. This idea is repeated on the subdominant, and then we move out of this introductory material and into a more extended, melodic passage. This passage sequences down the keyboard before briefly bottoming out on F minor, and then immediately sequences back up to the dramatic high point of this opening section – B-flat 7 (V/V), ultimately cadencing on E-flat major.

In broad strokes, I’d consider everything up until this the A section. Many of the basic musical ideas that will play out over the rest of the prelude are in place: introductory chords; a step-wise, descending melodic sequence; an ascending leaping sequence. 

Opening gambit 

Stepwise descending melodic sequence 

Leaping ascending sequence

This seems to be Bach’s general strategy: deploy the opening gambit for each new section of the prelude and branch off from there. Once we land in E-flat major, the second iteration of the opening gambit abruptly shifts back to A-flat major and leads into a relatively unstable few measures before landing on a stable idea.

The right hand builds up an arpeggiated chord while the left hand pulls down the keyboard. The widening gap between the hands creates a crescendo effect. 

Right hand builds up a chord; left hand travels down the keyboard. 

Bach repeats the idea twice more, each time landing in a darker harmonic area. The final iteration lands us solidly in F minor before losing steam through a slight chromatic, minor sequence that is accompanied by a fragmented bass line. This fragmentation leads into a section full of harmonic instability. Bach restates the opening material in minor and builds out a series of chromatically-inflected diminished chords. Functionally, this is clever because it creates a sense of tremendous instability while keeping the overall movement centered in F minor. Indeed, this is essentially a minor, extended iteration of the opening section. We hear a minor version of the stepwise melodic sequence that drifts down seemingly forever. After bottoming out at the low end of the keyboard, the leaping ascending sequence hauls the melodic material up and into A-flat major. Except it’s not A-flat major – an added seventh destabilizes the harmony and pulls us into D-flat minor. 

In what is probably the dramatic high point, the right hand repeats diminished iterations of the opening material, while the left hand has a series of the melodic, descending sequence.

Woo dramatic 

Eventually, the music does circle back to major, but harmonically things are not super stable. While we are hearing reasonably familiar material — quick ascending scales set against descending arpeggios — consistent chromatic inflections and relentless harmonic movements in each bar creates an unsettled feeling that once again ends with an A-flat 7 chord. Which is really odd – especially since we are approaching the end of the prelude, I would expect to be hearing a bunch of dominant harmonies, not a tonic-turned-dominant one. 

That’s pretty odd. 

The A-flat 7 chord marks the beginning of the end. But things stay pretty weird. Harmonically, things begin pointing in a more normative (if minor) direction — B-flat minor, an ambiguous F minor/A-flat major — before compressing into a diminished harmony and then resolving into a bizarre looking measure.


Upon closer inspection, this turns out to be B-double-flat major. Or, A major. This is a Phrygian flat–II  (also known as a Neapolitan) harmony. It only lasts one measure in the prelude before resolving to E-flat and then cadencing on the tonic. But, this harmonic movement acts as the main tether between the prelude and the fugue. As we’ll see, the fugue moves through a more extended, dramatic version of this same harmonic movement.

The Fugue

I loved learning this fugue. It was so much more interesting than I anticipated. The subject is stately but not stodgy. Sixteenth notes add some zing to the otherwise steady eighth notes, and the subject gradually picks up steam as we move through it. Melodically, there’s a sense of expansion over the first half of the subject — an opening third expands to a fifth and then to an octave — before compressing into running sixteenths that will later form the basis of the countersubject.

Fugue subject; the end of the subject expands into a countersubject.

The exposition begins with the two upper voices before working its way through the two lower ones. The bass is the last voice introduced. As the exposition ends, the bass continues the final idea from the subject and climbs up an unusually long sequence (seven repetitions!) before finally reaching a cadential gesture. 

This sequence lasts forever

The subject is reintroduced in the bass, accompanied by fragmented iterations of the previous sequential material in the upper voices. Essentially, we now have a countersubject, or a melodic idea that will now accompany the subject. It’s interesting that this countersubject’s material comes from the subject itself. It’s more common that the countersubject is made out of completely new, contrasting material. 

Like in the prelude, the minor section of this fugue is longer and more destabilizing than in many of Bach’s other works.  For example, after the subject is stated in C minor, we hear fragmented countersubject material bounce between the upper two voices before veering into E-flat minor. The soprano attempts a triumphant, major restatement of the subject in E-flat major. But, the lower voices subvert this modulation and instead dramatically pull the soprano into F minor. 

These two voices create an exciting tension – the soprano resolves while the alto begins a restatement of the subject

This is always one of my favorite parts – there’s just something exceedingly dramatic and compelling about the fight for auditory dominance between the soprano’s semitone pull into a cadence set against the restatement of the subject in the alto voice. 

After the alto wraps up this dramatic restatement, we come to an unusually long episode made up of long sequences of the countersubject. This idea passes through all of the voices in turn, systematically from high to low. After it passes through the bass, it’s then presented in thirds in the upper two voices set against the subject in the bass. Once again, there’s a heightening sense of instability due to increased chromaticism and constantly shifting harmonic movement. Unlike earlier in the fugue, this instability is not confined to just a few measures. It’s extended over several passages, each more unstable than the last, culminating with the bass dropping down to the lowest register of the keyboard and then dropping out completely. The upper two voices have an extraordinarily chromatic duet after which the tenor voice breaks in with a striking tonic restatement of the subject.

Bass goes low then drops out completely; the upper two voices have an extremely unstable, chromatic moment

And then the tenor tries restabilizing things with a tonic restatement of the subject.

Despite the tenor and then the bass providing tonic restatements of the subject, it’s still not enough to overcome the instability of what’s come before. After the bass finishes its reiteration — the last of the fugue — everything goes off the rails. The bass continues on with an inversion of the countersubject that sequences down, set against a series of blocked chords in the upper three voices. And they’re weird chords, too —we suddenly pull up a semitone from A-flat major into B-double-flat major (also known as A Major).

This whole section is bananas. So dramatic; everything just shifts up a half-step to the Neapolitan.

Eventually, A-major turns to a diminished chord, which allows Bach to resolve into the expected dominant seventh chord. Still unstable, but less unstable than what’s come before. And then, as if nothing unusual has just happened, Bach sets some diatonic scales in contrary motion and goes into an extended cadence.

Sure, let’s hang out for a while on an unresolved harmony and then pretend like nothing dramatic just happened.

It’s really quite odd, and a little funny. This fugue always sounded pretty dramatic when I listened to it, but I didn’t realize the extent to which this fugue is so harmonically unstable and unpredictable. All in all, I’d count this one as one of my favorites.