Fantasy Impromptu in C minor, Op. fast. 66, WN 46 – solo piano composition by Fryderyk Chopin. Despite Chopin’s instructions not to publish any of his unpublished manuscripts, it was published posthumously in 1855. Fantasia-Impromptu is one of Chopin’s most popular and frequently performed works. The Fantasia – Impromptu, like the Four Mazurkas (Op. 17) and the Grand Brilliant Waltz in E Major (Op. 18), was written in 1834, but unlike these other works, Chopin never published the Fantasia – Impromptu. Instead, it was published posthumously by Julian Fontana, along with other Opp waltzes. 69 and 70.
It is unclear why Chopin did not publish Fantasia-Impromptu. Parts of it were described as “sugary” and “devoid of nobility” by James Huneker. Ernst Oster has conducted a technical examination of the work, citing similarities between Fantasia-Impromptu and Ludwig van Beethoven’s Moonlight Sonata (Quasi una fantasia) as the reason for Chopin’s reluctance to publish it. It is also said to be reminiscent of Ignaz Moscheles’ Impromptu in E major, Op. 89, which was published in 1834, the same year Chopin wrote his Fantasia-Impromptu.
The mystery may have been solved in 1960, when pianist Arthur Rubinstein bought the “Album of the Baroness d’Este” at a Paris auction. The album included a manuscript of Chopin’s Fantasia-Impromptu, dated 1835, with the inscription in French on the title page “Composed for the Baroness d’Este by Frédéric Chopin.”
Rubinstein considered the fact that its authenticity had been “guaranteed by the French authorities” and that it demonstrated “delicate care for detail” and “many improvements in harmony and style” over the previously published version to be absolute proof that it was a finished work. Rubinstein suggests in his preface to The Rubinstein Edition, published by G. Schirmer, Inc. in 1962, that the words “Composed for” rather than the dedication imply that Chopin received a paid commission for the work, implying that he actually sold it to the baroness.