In music, a prelude is a short piece, usually in no particular form.
An instrumental prelude was originally a short extemporised piece of music played before the piece to be performed. It developed out of the musician's natural tendency to play a few notes on his instrument before commencing, and eventually became a recognised art form in its own right, with publishers advertising books of pre-written preludes appearing in the 17th century.
Frederic Chopin and Sergei Rachmaninov wrote preludes for the piano in all twenty-four keyss.