Issues : Last key signature sign

b. 5

composition: Op. 28 No. 14, Prelude in E♭ minor

c-c1 w A, literal reading (→FE,FCGE1)

c-c1 in EE, GE2 (→GE3) & FES

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The missing naturals raising c-c1 to c-c1 are almost certainly Chopin's mistake. It is indicated by the naturals added by Chopin in FES as well as by the cautionary  written in A before c1 in the next bar (eventually crossed out), which suggests that Chopin assumed that it was c that was valid there*.
The naturals were added in EE and GE2 (→GE3).


* A precautionary approach should be taken in the case of a reasoning based on a cautionary accidental – in b. 12 in A we can also observe crossed-out flats before c-c1, although the sound of those notes had already been consolidated at the beginning of b. 10 (Chopin was not always certain which accidentals were included in the key signature).

category imprint: Interpretations within context; Differences between sources; Source & stylistic information

issues: Annotations in teaching copies , EE revisions , GE revisions , Omission of current key accidentals , Deletions in A , Annotations in FES , Last key signature sign

b. 6

composition: Op. 21, Concerto in F minor, Mvt I

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In the main text we omit the superfluous flats before the D-d octave.

category imprint: Editorial revisions

issues: Cautionary accidentals , Last key signature sign

b. 6

composition: Op. 50 No. 3, Mazurka in C♯ minor

..

Both autographs are lacking in the  raising a1 to a1. The mistake is also in EE, where it was repeated after the proof copy of FE. In the very FE Chopin added the overlooked accidental; the correct text is also in GE.

category imprint: Interpretations within context; Differences between sources

issues: Errors of A , Authentic corrections of FE , Last key signature sign , Errors repeated in EE

b. 6

composition: Op. 28 No. 7, Prelude in A major

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In the main text we omit the unjustified cautionary  before g1, featured in all sources.

category imprint: Editorial revisions

issues: Cautionary accidentals , Last key signature sign

b. 7-8

composition: Op. 25 No 6, Etude in G♯ minor

No accidentals in FC (→GE1), FE & EE

Naturals in GE2 (→GE3)

Naturals suggested by the editors

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In front of the 2nd semiquaver in each of these bars, there are no accidentals in the sources except for naturals added in GE2 (→GE3), which cannot come from Chopin. Therefore, it seems that the top note is supposed to be a2. However, there are strong grounds, both source (proved also in other pieces Chopin's doubts concerning the notation of a/a notes in the G minor key) and stylistic (natural harmonic passage), for considering it as Chopin's mistake. Therefore, in the main text we suggest to add naturals to achieve the sound of a2.

category imprint: Interpretations within context; Differences between sources; Editorial revisions

issues: Errors in FE , Errors in EE , Errors in GE , GE revisions , Last key signature sign , Errors of FC