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b. 2-4

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

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In AB all L.H. octaves starting from D1-D are written in an abridged manner with the con 8va indication.

category imprint: Source & stylistic information

issues: Abbreviated octaves' notation

b. 9-12

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

13 bars in A (→FCGE, →FEEE), #ASch & CGS

9 bars in AB

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Initially, the Prelude had only 9 bars, which is proven by the footnote in A according to which b. 9-12 were added at the suggestion of certain "Mr. xxx." The Prelude in its initial, 9-bar form can be found in AB, written a year after the entire Op. 28 had been finished.
In A (→FC) the discussed bars are marked in an abridged manner as a repetition of b. 5-8 (mentioning the different dynamics).

category imprint: Differences between sources; Corrections & alterations; Source & stylistic information

issues: Abbreviated notation of A , Changed phrase length