Frédéric Chopin's Allegro de concert, Op. 46, is a piece for piano, published in November 1841. It is in one movement and takes between 11 and 15 minutes to play. The principal themes are bold and expressive. It has a curious place in the Chopin canon, and while its history is obscure, the evidence supports the view, shared by Robert Schumann and others, that it started out as the first movement of a projected third piano concerto, of which the orchestral parts are either now non-existent or were never scored at all. There is no evidence that Chopin ever even started work on the latter movements of this concerto.
The above text from the Wikipedia article "Allegro de concert (Chopin)" text is available under CC BY-SA 3.0.