The word impromptu was first used as a title for a musical composition in 1822 by the Bohemian composer Vorisek for six piano pieces, to be imitated by Schubert's publisher in naming a set of four piano Impromptus, to be followed by four more, perhaps so named by the composer. Chopin used the title for four compositions in this seemingly improvised form, and there are further impromptus by other composers from that period onwards, generally, but not always, for a single instrument.