# Bwv 999



## beetzart (Dec 30, 2009)

I have enjoyed playing this little JS Bach prelude for many years but it is rather bizarre. It is in, or starts in, C minor, yet ends in G major. I'm not a musicologist but can anyone explain how he manages this amazing modulation? I just stare at the notes and I can't figure out how he does it.

https://imslp.org/wiki/Prelude_in_C_minor,_BWV_999_(Bach,_Johann_Sebastian)


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## Eschbeg (Jul 25, 2012)

In m. 11, Bach introduces vii∘7 of G minor (the fleeting appearance of D in the next measure momentarily turns the chord into a V9 of G minor), which resolves as expected to G minor in m. 13. It's a pretty routine modulation, actually. More unexpected is the move from G minor to G major: rather than save that change for the end (i.e. a Picardy 3rd), Bach just casually uses B-naturals in place of B-flats in m. 34.


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## ldiat (Jan 27, 2016)

and her is a another answer from a Person on twitter i asked Her:

Here's my take: m.7 is the last time it's solidly in C minor. M.8 uses a passing tone in the bass to move to A-flat for m.9--even though the G is still present, the bass is overriding it a bit to make A-flat major, which is the Neapolitan chord in G minor...


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## Guest (Jul 16, 2018)

Eschbeg said:


> In m. 11, Bach introduces vii∘7 of G minor (the fleeting appearance of D in the next measure momentarily turns the chord into a V9 of G minor), which resolves as expected to G minor in m. 13. It's a pretty routine modulation, actually. More unexpected is the move from G minor to G major: rather than save that change for the end (i.e. a Picardy 3rd), Bach just casually uses B-naturals in place of B-flats in m. 34.


This is it.

Also, the exchange of notes from the major mode is pretty unusual in this period of history for anything except for a picardy third at the end of the piece. I wouldn't be surprised if Bach intended this piece to be played before some other c minor composition, as ending in the dominant key is still _unstable_ despite being temporally distant from the c minor opening. Playing something in c minor after this prelude will imply a release of tension that you wouldn't even realise was there, such is the genius of Bach.


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## ldiat (Jan 27, 2016)

and this from twitter:
Could you see this as a disguised cadence where Bach wanted the listener to think that the G minor chord in 12 was pulling to the dominant in C minor (v-V-V7) but never does? Seems like a pretty cool ninja move that I may have to steal…


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