Charles-Valentin Alkan wrote 25 preludes for solo piano or organ in 1844; they were published as his Op. 31 in 1847. These preludes span all 24 major and minor keys, plus an additional 25th prelude in C major.
"We must not expect to find in this artist's volume of preludes a flurry of fast notes by means of which certain pianists presage the skill before the performance of a piece. Alkan is a person of heart and mind; his preludes are dream-like which conceal a very calculated and finished art form."