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b. 3

composition: Op. 28 No. 20, Prelude in C minor

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We add cautionary naturals before d and d1. The accidentals were also added in EE.

category imprint: Differences between sources; Editorial revisions

issues: EE revisions

b. 3

composition: Op. 28 No. 20, Prelude in C minor

e1 in A (literal reading→FE,FCGE), AB & EE2

e1 in ACh, CGS, EE1 & FES

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According to us, it is much more likely that the missing  restoring e1, which would result in e1 at the end of the bar, is one of numerous such oversights of Chopin – see, e.g. the note to b. 8 and 12 as well as to the Prelude No. 7 in A Major, b. 13 or No. 18 in F Minor, b. 8. Therefore, we assume that the flats entered or added in ACh, CGS and FES define or restore the only correct text, which we adopt as the main one. However, the version with e1 has a consistent place in the history of music, e.g. as the theme of variations of Feruccio Busoni (BV 213a) and of Sergei Rachmaninoff (Op. 22).
The double revision in EE is noteworthy – first a  was added in EE1 and then it was removed in EE2.  

category imprint: Differences between sources

issues: Annotations in teaching copies , EE revisions , Omissions to cancel alteration , Errors of A , Annotations in FES

b. 3

composition: Op. 28 No. 20, Prelude in C minor

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There is no  restoring b in the 2nd chord in AB, which is a patent oversight.

category imprint: Differences between sources

issues: Omissions to cancel alteration

b. 5

composition: Op. 28 No. 20, Prelude in C minor

..

We add a cautionary  before a1 in the main text.

category imprint: Editorial revisions

b. 6-10

composition: Op. 28 No. 20, Prelude in C minor

..

In the main text we add cautionary naturals before the F-f octave in b. 6 and 10.

category imprint: Editorial revisions