Lack of accidentals before the 5th pair of quavers in A (→FE→EE3) means that Chopin forgot to put either a 
next to the 9th quaver (a1) or a 
next to the upper note of the following sixth (a2). The former possibility seems to be much more likely:
- such errors belong to the most common ones in case of Chopin (see the issue "Omissions to cancel alteration");
- in the scale melodic passages of this Etude Chopin would insert chromatic tones between the tones of the current key and not instead of them;
- in analogous bar 35 the returning d2 was added, probably by Chopin, in the last proofreading of FE (→EE).
The revisers of GE and EE4 added a before the upper note of the sixth.
Compare the passage in the sources »
category imprint: Interpretations within context; Differences between sources
issues: EE revisions, GE revisions, Errors of A
notation: Pitch
