Is this chord from Bach's C major Prelude G+ or Cm?

Question

So I'm analyzing the harmony in Bach's C major Prelude from the Well Tempered Clavier, and it all goes smoothly until I reach this chord:

Now, most editions I see of this Prelude don't have this chord in it. I even have 2 piano books that both have this Prelude and they differ by exactly 1 bar because one of them has this chord in it and the other one doesn't, it just has the 2 diminished sevenths right next to each other. That doesn't necessarily mean that one or the other is wrong though, as I have seen happen with 2 editions of Mozart's K545 in the past, where the Andante in one edition had a false recapitulation before repeating the G minor and the majority of the others went straight to the G major with no false recapitulation whatsoever. So I treated it as though it was correct. And also, I was just curious about how I should go about analyzing a chord like this one.

If it is correct though, what chord is it? G, B, C, Eb, that spells a minor-major seventh chord on C, but that kind of seventh chord isn't used in Classical Music, so it's probably a triad with an added non-chord tone. But which triad? It could be G+, that certainly fits with how the chord sounds, calling it an augmented triad on the dominant. But, do augmented triads even get used at all in the Baroque? Earliest composer I have seen use an augmented triad is Beethoven and it doesn't become common until the Romantic Era with composers like Chopin and Liszt. Also, I wouldn't expect an augmented triad to move to a diminished seventh chord directly. I would expect it to move to either a major or minor triad by moving one of the notes by a half step up or down and then for the triad to go to a diminished seventh if I indeed see an augmented chord going to a diminished seventh.

The other option is that this could be a C minor triad with a non-chord tone B. That fits better with the diminished chords preceding and following it and with the style in general. I don't know though, I hear an augmented triad more than I do a minor triad in there.

This is what my analysis looks like with the mystery chord included:

Without that chord, the first of the 2 diminished sevenths is vii°7/V and the second is vii°42 of the tonic C major. With the mystery chord though, the vii°7/V becomes a Ct°7, because the Eb is a common tone. And so is the C if the mystery chord is a C minor triad with a non-chord tone B.

So, what chord is this? Is it the G augmented chord that it sounds like when I play it? Or the C minor triad that fits better with the style and the diminished chords?

Answer 1

This measure is called the "Schwencke measure" as it was supposedly inserted by Christian Schwencke. Modern music historians (mostly) believe that the measure was inserted incorrectly. This measure is not in Bach's autograph copy.

There are speculations as to how it got added. The harmonic analysis from the attached article calls the chord a C-minor 64 with a major seventh. Among the speculations as to why it was inserted include "having a better bass line" or "filling out the 4-measure patterns common in the rest of the piece."

https://www.henle.de/blog/en/2012/04/16/on-the-lookout-for-the-lost-measure-bach%E2%80%99s-c-major-prelude-from-the-well-tempered-clavier-i/

Answer 2

In the original version by Bach, without this measure: --

We have a very quiet and childlike beginning to this prelude, which touches all the expected bases and reaches a cadence at bat 19. A lesser composer would just move on to the fugue, but Bach wants to do some more interesting things, so he visits some darker and much more dramatic areas with color drawn from the parallel minor. He starts this with a V7/IV-IV, which at first just seems like the idea he's already presented at bars 8 and 16: we have a dominant going to a tonic, but the leading tone's resolution gets delayed. If this was going to be a boring, literal repetition of that idea, then we'd simply have another ii-V-I in C, exactly recapitulating the harmony of bars 16-19. Instead, he throws in the drama and weirdness. The drama is that he gives us what sounds like a viio7/V at bar 22. This sounds like, OK, we're going to hear a variation on the previous material, drawing on the parallel minor for color. But then all hell breaks loose, and he gives us another diminished seventh, this time built on the root a half-step above the dominant. Crazy. I think I've heard this described as "surrounding" a note: you approach it from both a half-step below and a half-step above. Then the light clears and we get to the G dominant, and the rest is pretty standard.

In Schwencke's version: --

It's easy to see why Schwencke felt the need to "fix" this. The musical traditions were based on vocal music, in which you don't really expect singers to be happy about singing an interval from F# to Ab. The ideal is that a line is supposed to be singable. So Schwencke inserts another bar in which the imaginary "singers" get a G, so the line goes F#-G-Ab-G. This is a lot more singable, and therefore "better" in some sense. Trying to force this all into a framework of triads is beside the point. That isn't the way people in Bach's time thought. They thought in terms of voice leading. If you want to give Schwencke's chord a harmonic analysis, then I would call it a V chord with two suspensions (the C and Eb). Then the C resolves to a B, the Eb goes up to an F, and we have pretty normal dominant seventh harmony, except that the Ab in the bass makes it a diminished 7th sonority instead of a seventh chord.

In Schwencke's chord, I don't think the B has a harmonic function. It's just a neighboring tone of the C in the chord. Augmented and minor-major-7th chords were not a thing in this era.

Answer 3

Now, most editions I see of this Prelude don't have this chord in it. I even have 2 piano books that both have this Prelude and they differ by exactly 1 bar because one of them has this chord in it and the other one doesn't, it just has the 2 diminished sevenths right next to each other. That doesn't necessarily mean that one or the other is wrong though, as I have seen happen with 2 editions of Mozart's K545 in the past, where the Andante in one edition had a false recapitulation before repeating the G minor and the majority of the others went straight to the G major with no false recapitulation whatsoever. So I treated it as though it was correct.

I'm going to stop you there and say the rest is moot, because this bar is (for want of a better word) wrong.

To quote the 1994 ABRSM edition (edited by Richard Jones with commentaries taken from the earlier 1924 Tovey edition)

[Tovey] The bar added by Schwenke between bb.22 and 23 shows the danger of misunderstanding one of Bach's most characteristic progressions, the skip in the base from F# to Ab, avoiding striking the dominant until the long pedal-point begins. Probably Schwenke thought it desirable to have an even number of bars before reaching this point; this is, however, not necessary.

[Jones] This bar was added subsequently [to Bach's version 1722-1732] in CFG Schwenke's MS copy of 1783 (M3) and incorporated in his edition of 1801 (V). Almost all other 19th-century editors followed suit before Franz Kroll's Peters edition appeared in 1862

Bach didn't write it. Let's not trouble ourselves with analysing it.

Answer 4

In addition to the answers that mention the chord by Schwenke we can say quite clearly: this is not a V #5 chord G,B,D#). Bach moves to the parallel minor (Cm64=G,C,Eb) - analogous passage in Cm prelude m. 21 - and B is just the lead tone used as chromatic approach to C.

Answer 5

We don't know Bach didn't write the measure, no matter who says it. It could easily have been from a lost manuscript. Music history isn't especially scientific compared to say world history or human history. And the more less famous pieces by Bach you listen to, the more you realize how colorful he can be. First, harmonic analysis isn't particularly appropriate for Bach because it's harmony resulting from counterpoint. Bach will never write bad counterpoint. That said, besides the notes themselves, look at which notes fall on the beat, so are technically more important, and not ornaments. Also look at which notes patterns constitute ornaments in the Baroque. Then you will be able to at least support an argument, whether it's right or wrong... When all else fails (or maybe it should be the first thing) what does the tonality sound like -- there's a big difference in sound between minor and augmented