In bar 17 we add cautionary naturals before f1 and f2. In bar 19, in a similar situation, the signs are already included in A.
In bar 17 in A there is a visible trace after the change of the lower note of the 3rd chord in the R.H. from g
1 to f1. Chopin introduced similar changes also in bars 19 and 21. Cf. bar 22.
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category imprint: Editorial revisions; Corrections & alterations
issues: Corrections in A, Cautionary accidentals
notation: Pitch