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b. 17

composition: Op. 10 No 6, Etude in E♭ minor

Doubled f in A (→FEEE,GE1GE2)

Single f in GE3 (→GE4GE5)

..

The omission of the additional semiquaver on the last note is most probably an oversight of the engraver of GE3 (→GE4GE5).

category imprint: Differences between sources

issues: Errors in GE

b. 18

composition: Op. 10 No 6, Etude in E♭ minor

..

In A (→FEGE1GE2GE3GE4) there is no  raising c1 to c1 in the chord at the beginning of the bar, which must be an error. Chopin added the necessary sign in FED (as well as the second one "on the run", unnecessary before in the 2nd half of the bar). The correct text is included also in EE and GE5.  

category imprint: Interpretations within context; Differences between sources

issues: Annotations in teaching copies , EE revisions , GE revisions , Omission of current key accidentals , Errors of A , Annotations in FES

b. 18

composition: Op. 10 No 6, Etude in E♭ minor

..

Before the 1st chord we add cautionary flats before a and a1.

category imprint: Editorial revisions

b. 18-19

composition: Op. 10 No 6, Etude in E♭ minor

..

In A (→FE) Chopin omitted the naturals raising B1 to B1C to C and c to c. The second of them was added in FES. In GE was added at the end of bar 18, yet both signs in bar 19 appeared only in GE3 (→GE4GE5). EE has the correct text. 

category imprint: Interpretations within context; Differences between sources

issues: Annotations in teaching copies , EE revisions , Accidentals in different octaves , GE revisions , Omission of current key accidentals , Annotations in FES

b. 20

composition: Op. 10 No 6, Etude in E♭ minor

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We add cautionary flats before b and b1. The accidentals were added in GE4, yet in GE5 some of them were overlooked.   

category imprint: Differences between sources; Editorial revisions

issues: GE revisions