Various editions of Mozart’s piano sonata K. 457, including the New Mozart Edition, comment on this seeming anomaly at X (circled in m. 209) in the last movement:
- Mozart K 457.3.png (1.63 MiB) Viewed 24889 times
- Mozart K 457.3 A.png (37.82 KiB) Viewed 24891 times
1. Mozart rarely mispositions a note head.
2. Two mistakes are required here, the badly placed note head and the omission of a sharp. Mozart does occasionally omit accidentals. But two mistakes at once?
3. If the pattern from the previous measures is to be maintained, why did he write an F as the first note of the measure rather than an E#? Is that also an error? Three errors in one measure?
Based on the following reasoning, I believe that no error occurs here in the manuscript and that the measure is correct as written:
Each of the four similar measures leading to m. 209 contains one principal melody note surrounded by neighboring tones. But measure 209 contains two melody tones, F and F#, and no neighboring tones. The F holds over from the previous measure so that it can fall with the A flat bass tone to complete an F minor chord, which is the iv that will lead eventually to V. It is a chord tone not a decoration and therefore must be written as an F:
- Mozart K 457.3 B.png (41.47 KiB) Viewed 24891 times
But why not use the E# to decorate the F# later in the measure? Here Mozart was faced with a difficult choice. If he writes an E# (=F), there is a danger that one will hear this as a repeat of the opening F — F# and iv6 — #iv6/5. We would suddenly have four melody notes and four harmonic changes in the measure, which is out of keeping with the rest.
- Mozart K 457.3 C.png (32.68 KiB) Viewed 24891 times
Mozart makes his choice, which I think is the best given the situation and one that should be respected in performance.
A more complete analysis follows. The first example shows the symmetrical nature of the passage (bracketed) and Mozart's omission of a measure through ellipsis:
