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b. 26

composition: Op. 10 No 12, Etude in C minor

..

In A there is no cautionary  before c. The accidental was added in a proofreading of FE (→GE,EE). In the main text we add yet another one before the 7th note (in view of the C in the R.H. chord).

category imprint: Differences between sources; Editorial revisions

issues: Cautionary accidentals , Authentic corrections of FE

b. 27

composition: Op. 10 No 12, Etude in C minor

Dotted rhythm in A

Semiquavers in FE (→GE,EE

..

Chopin changed the rhythm of A while proofreading FE (there are visible traces of this change). The withdrawal from the rhythmic underlining of the topmost note of the passage may be related to a minor change in the Etude's concept, revealed also in increasing its tempo. See also bars 30 and 32.

category imprint: Differences between sources; Corrections & alterations

issues: Authentic corrections of FE , Dotted or even rhythm

b. 27-28

composition: Op. 10 No 12, Etude in C minor

Fingering in A

Fingering in FE (→GE)

Fingering in EE

Our variant suggestion

..

Bar 27 is one of two bars in which the fingering is already included in A. It was repeated and completed in FE (→GE,EE), yet with one exception – the last digit in A is written under the penultimate note and in the editions – under the last one. According to us, the engraver's error is a more possible explanation than Chopin's correction. Therefore, in the main text we consider both possibilities, however, we give preference to the undoubtedly authentic version of A.
In EE one digit was added. 

category imprint: Interpretations within context; Differences between sources

issues: EE revisions , Authentic corrections of FE

b. 27

composition: Op. 10 No 12, Etude in C minor

 in A

No marking in FE (→GE,EE

Our variant suggestion

..

In the further part of the bar Chopin performed corrections in FE, the omission of  at the beginning of the bar seems to be however the engraver's oversight.

category imprint: Differences between sources

issues: Errors in FE

b. 27

composition: Op. 10 No 12, Etude in C minor

  in A

FE (→GE,EE

..

In the main text we reproduce the dynamic hairpins after A. In the editions their range underwent a minor change, which can be however considered to not be devoid of meaning.

category imprint: Differences between sources

issues: Inaccuracies in FE