Impromptu, for chamber orchestra, op. 87a

The Impromptu, Op. 19, is a single-movement work for female choir and orchestra written in 1902 by the Finnish composer Jean Sibelius. The piece, which is a setting of the Swedish poet Viktor Rydberg's poem Unge hellener (Young Hellenics), premiered in Helsinki on 8 March 1902, with Sibelius conducting the Helsinki Philharmonic Society and an amateur choir. The Impromptu was the middle item a program that also included two other first performances: the Overture in A minor (JS 144), which served as the opener; and the Second Symphony (Op. 43).

Sibelius extensively revised the Impromptu in the spring of 1910, reducing the instrumentation and altering both the beginning and ending of the piece, the former of which now incorporated a second Rydberg poem, Bacchospräster (The Priests of Bacchus). This version of the Impromptu received its premiere in Helsinki on 29 March 1912, with Sibelius conducting the Philharmonic Society; "Nuori Laulu" and the Arbetets vänner female choir sang the choral part.