It is a short, usually without a specific internal structure, work that can serve as an introduction to subsequent parts of a larger and more complicated work. In its beginnings, preludes were instrumental improvisations. The oldest surviving preludes date back to the 15th century, and starting from the 17th century they were pure improvisations, not related to other works. Nevertheless, it is in the 18th century that the prelude becomes an important musical form, as it is combined with a fugue, resulting in many masterpieces including those by Johann Sebastian Bach. In classicism, the prelude is partially forgotten, but it returns with romanticism, mainly thanks to Brahms, Liszt, and Mendelssohn. In this era, self-contained preludes also appear, mainly for the piano, with Chopin being an excellent creator of them. A little later, Debussy and Rachmaninoff also created such preludes.
BAROQUE
Johann Sebastian Bach Prelude and Fugue in C major - Helmut Walcha