Via wikipedia: During the Classical era, C minor was used infrequently and always for works of a particularly turbulent cast. Mozart, for instance, wrote only very few works in this key, but they are among his most dramatic ones (the twenty-fourth piano concerto, the fourteenth piano sonata, the Masonic Funeral Music, the Adagio and Fugue in C minor and the Great Mass in C minor, for instance). Read more...