About Frédéric Chopin's Impromptus
The term Impromptu, fashionable for a short time in the first half of the 18th century, designates a free-form composition, for the most part highly organized, but retaining something of the sense of being the result of a sudden inspiration.
Some have suggested that Chopin thought of his four Impromptus as a "set" in which each successive impromptu is derived from the previous one.
One should remember, however, that they appeared several years apart, and that the fourth and last in publication was the first to be composed.
This work, named Fantasie-Impromptu, has become the most famous of the group – ironically enough, since Chopin asked that it should be destroyed after his death.