FES
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On the 8th quaver in A and FE there is no natural returning f1. In analogous bar 17 Chopin corrected his mistake, adding the natural in the pupils' copies FEJ and FES. The sign was added in GE and EE.
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See b. 17
category imprint: Interpretations within context; Differences between sources
issues: Omissions to cancel alteration
notation: Pitch