Newly engraved 2000 Edition with larger notation for easier reading. Chopin's 24 Preludes, Op. 28, are a set of short pieces for piano, one in each of the twenty-four keys, originally published in 1839. The Prelude in C-sharp minor, Op. 45 (sometimes listed as Prelude No. 25), was composed in 1841. Although the term prelude is generally used to describe an introductory piece, Chopin's preludes stand as self-contained units, each conveying a specific idea or emotion.