How did Robert Schumann turn his piano fantasy into the Piano Concerto in A Minor?

The Piano Concerto in A Minor, Op. 54, by German composer Robert Schumann, originated as a one-movement fantasy for piano and orchestra. This initial version premiered in 1841 with his wife, Clara Wieck Schumann, as the soloist and Felix Mendelssohn conducting.1

Four years later, in 1845, Schumann expanded this fantasy into a full-fledged, three-movement concerto. He retained the original fantasy as the basis for the expansive first movement, titled "Allegro affettuoso," while adding two new movements: a songlike "Intermezzo" and a vibrant "Allegro vivace" finale. While Schumann sometimes struggled with large-scale orchestral development, the piano's central role in this work helped him successfully bridge his intimate musical style with the demands of a larger concerto form.12