The most well-known example of esoteric accidentals in Chopin’s music occurs at the end of the first section of the Etude op. 25 no. 10. This piece is in a A-B-A form with a serene middle section in B major surrounded by stormy octave sections in B minor.

- Chopin Etude op 25 no 10 Notatio example 1A.jpeg (152.41 KiB) Viewed 13828 times
The area at * has even been held up to ridicule as absurd, and many have proposed the simpler spelling:

- Chopin Etude op 25 no 10 Notatio example 1B.jpeg (70.27 KiB) Viewed 13828 times
So why did Chopin write what he did?
As shown in the following example, Chopin is making a seamless connection between the first and second sections, no easy feat considering the drastic change involved. The solution is simplicity itself. The first part ends with three repetitions of an underlying pattern “x” shown at ** which breaks a F

dominant seventh chord, the V7 of the piece, into a scale-wise series of thirds. On the final repetition, the last two thirds E-C

D (#)-B are withheld until after a sudden interruption, and only appear in the new meter and tempo and mode, thus bridging the gap with a single chord.

- Chopin Etude op 25 no 10 Notatio example 2B.jpg (253.08 KiB) Viewed 13826 times
To create the sudden interruption, Chopin decorates the F

7 with a a neigboring tone harmony, E

diminished seventh, which represents the dominant of F

. This chord in turn is transformed and connected back to the F

7 by means of one of those complex multi-layer modulations that Chopin is famous for. This is shown at **** in the example.
Crucial to this modulation is the transformation of the E

diminished seventh chord into a dominant seventh chord by means of ellipsis: replacing the G

with the passing tone G

as shown at *** so that it can become a F

and lead as part of a V7 to the apparent key of B

, which is itself a harmonized passing tone between the B in the E

dim. 7 and the C

in the F

7. Because of the complexity of this progression, it is crucial that the bass tone E

be shown as a neighboring tone to F

throughout, and not as an F

, or the overall F

-E

dim 7-F

progression would become lost to view. At the same time he must also show that the new sub-harmonies constitute a series of descending fifths V7-I-IV7 within the new key of B

. The following notation would have preserved some of this, but aside from its awkwardness, it would misrepresent the B# as a C, and the B# major chord as a structural

II6 in B minor, which it is not.

- Chopin Etude op 25 no 10 Notatio example 1C.jpeg (76.34 KiB) Viewed 13828 times
Or better, he could have used the following notation for the initial F

7 chord, which supplies the rest of the “missing” altered E

diminished seventh chord. Perhaps he should have, given the universal antipathy to the notation as it stands. Yet despite using such enharmonic tieing in other pieces, he decided against it here, probably fearing to add additonal complexity to an already complex passage.

- Chopin Etude op 25 no 10 Notatio example 1D.jpeg (74.13 KiB) Viewed 13828 times
Note that the slur in ms. 2 and 3 of the first example leads directly to the A

in the F

7 chord to complete the first and second thirds of of pattern x: A

-C

D-B (=A

). Chopin probably hoped that this slur would alert the player to the fact that the A

stands-in for an understood B, before it is transformed into an A

so that it may become the leading tone in the key of B

major.
Another interesting notational feature occurs in m. 4 of the initial example. There are only three quarter notes in this final 2/2 measure! This anomaly was retained in the first and later editions. More recent editions cannot restrain themselves from correcting Chopin’s “mistake” and make the quarter rest, a half rest. When one understands the first measures of the Lento are actually the last part of pattern x, it becomes clear that Chopin would want only a small pause between the A and B sections. For that reason and for metric assonance, the 3/4 actually occurs one measure earlier than notated, and forms an additional bond between the sections. Actually placing the 3/4 meter change in the previous section would be visually disruptive, however, since the new mood is achieved only at the Lento. Thus Chopin’s solution, which was probably entirely intuitive, disturbs no one, provides interpretive help, and should be left as it stands.