Frédéric Chopin composed this Mazurka in A flat major around 1834. It is a somewhat obscure piece, with no known dedicatee, and published posthumously in 1930 (it is noteworthy that Chopin had requested that his unpublished works be burnt upon his death). As it doesn't have a proper Opus number, it is usually referred to as B. 85, and KK IVb/4, according to its entry numbers in the Brown and Kobylanska catalogues respectively.
