Felix Mendelssohn Bartholdy: LMA I/4a:

In the 19th century it was perfectly customary to arrange symphonies for chamber settings, which gave them a greater chance of being performed. Felix Mendelssohn Bartholdy created two versions of his C minor Symphony Op. 11, both of which are now available: the first is the version heard in London in 1829 (with the Scherzo from the Octet Op. 20) in a dazzling chamber version for piano duet with violin and violoncello ad libitum; the second is the well-known piano version (for four hands) written in 1824 and published ten years later (with Minuet), which is closer in character to a piano reduction.