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b. 1

composition: Op. 25 No 7, Etude in C♯ minor

..

In GC (→GE1) and EE there is no  returning f at the beginning of the 2nd group of semiquavers of the introduction, which almost certainly corresponds to the notation of [A]. It is a very typical mistake of Chopin – cf., e.g., the Nocturne in Cminor, Op. 27 No. 1, bar 83, or the Impromptu in A major, Op. 29, bar 71. The sign was added in the proofreading of FE, most probably by Chopin, as well as in GE2 (→GE3). 

category imprint: Interpretations within context; Differences between sources

issues: Errors in EE , Omissions to cancel alteration , Errors in GE , GE revisions , Authentic corrections of FE

b. 1

composition: Op. 25 No 7, Etude in C♯ minor

..

We add a cautionary  before b. A similar addition was already added in GE and EE.

category imprint: Differences between sources; Editorial revisions

issues: EE revisions , GE revisions , Cautionary accidentals

b. 3

composition: Op. 25 No 7, Etude in C♯ minor

..

The cautionary  before was added in EE and GE2 (→GE3).

category imprint: Differences between sources; Editorial revisions

issues: EE revisions , GE revisions , Cautionary accidentals

b. 12

composition: Op. 25 No 7, Etude in C♯ minor

..

All sources, except for GE2 (→GE3), include an additional  before c1 in the bottom voice. It can be a remnant of the hypothetical original notation, in which the two previous thirds were written as c1-e1. Following the second German edition, we do not consider this superfluous sign in the main text. 

category imprint: Differences between sources; Editorial revisions

issues: GE revisions , Cautionary accidentals

b. 15

composition: Op. 25 No 7, Etude in C♯ minor

..

In GC and FE there is no  lowering c to c. This patent inaccuracy was corrected in GE and EE.

category imprint: Interpretations within context; Differences between sources

issues: EE revisions , Errors in FE , GE revisions , Omission of current key accidentals , Errors of GC