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Pitch

b. 7-11

composition: Op. 28 No. 20, Prelude in C minor

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In the main text we add cautionary flats before the a-a1 octave in b. 7 and 11.

category imprint: Editorial revisions

b. 8-12

composition: Op. 28 No. 20, Prelude in C minor

d1 in A (literal reading→FC,FE) & CGS

d1 in AB, ACh, GE, EE & FES

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The missing  restoring d1 is almost certainly an oversight of Chopin in A (→FC,FE), which is proven by the naturals in AB, ACh and the one added in b. 8 in FES. The accidentals were also added by the revisers of GE and EE.

category imprint: Interpretations within context; Differences between sources

issues: EE revisions , Omissions to cancel alteration , GE revisions , Errors of A , Errors repeated in FE