Published posthumously in 1855, the Fantaisie Impromptu In C# Minor Op. Post.66 is one of Chopin#s most frequently performed and popular compositions. There was initially some mystery surrounding the piece and why Chopin never published it during his lifetime. James Huneker, trying to explain why the piece was not published, calls parts of it "mawkish" and "without nobility", whilst Ernst Oster writes that a technical exploration would show why Chopin did not publish the work, and that exploration shows that the Fantaisie-Impromptu and Beethoven's Moonlight Sonata ("Quasi una fantasia") are related. The mystery may have been solved in 1960 when pianist Arthur Rubinstein acquired the "Album of the Baroness d'Este" which had been sold at auction in Paris. The album contained a manuscript of the Fantaisie-Impromptu, written in Chopin's own hand and dated 1835. The title page for the manuscript states that the piece was "Composed for the Baroness d'Este by Frédéric Chopin" and from this Rubinstein surmises that the words "Composed for" in place of a dedication imply that Chopin received a paid commission for the work. This Henle Urtext Edition for solo Piano has been edited by Ewald Zimmermann and includes fingering by Hans-Martin Theopold.