Symphony No. 5, Op. 50 is a symphony written by the danish Carl Nielsen between 1920 and 1922; it was first performed in Copenhagen on 24 January 1922 with the composer conducting. It is one of the two of Nielsen's six symphonies lacking a subtitle. The Fifth Symphony has a non-customary structure, comprising two movements instead of the common three or four. Written in a modern musical language, it draws on the theme of contrast and opposition. The post-World War I composition is also described to contain elements of war.
The Fifth Symphony has two movements (Tempo giusto-Adagio non troppo/Allegro-Presto-Andante un poco tranquillo-Presto) instead of the usual four, which is the only time Nielsen used this structure. Nielsen explained jokingly in an interview that it was not difficult to write the first three movements of a symphony but by the finale most composers had run out of ideas. The work has a craggy profile as "it is littered with false climaxes at every turn". In summary, the first movement is a battle between the orchestra and a renegade snare-drummer, who can only be silenced by the full forces of his colleagues in the final bars. The second movement continues the struggle with shivers of anxiety, building through repetitions and detours to the final victorious grand explosion. Though bearing no title, Nielsen affirmed that the Fifth Symphony, like his previous symphonies, presents "the only thing that music in the end can express: resting forces in contrast to active ones." In a statement to his student Ludvig Dolleris, Nielsen described the symphony as "the division of dark and light, the battle between evil and good" and the opposition between "Dreams and Deeds". To Hugo Seligman he described the contrast between "vegetative" and "active" states of mind in the symphony. As such, the symphony is widely stated to be a work about contrast and opposition. The composer asserted that he was not conscious of the influence of World War I when composing the symphony, but added that "not one of us is the same as we were before the war." Simon Rattle also described the Fifth Symphony, rather than the Fourth as proclaimed by the composer, as being Nielsen's war symphony. In fact, the phrase "dark, resting forces, alert forces" can be found on the back cover of the pencil draft score. Nielsen might have considered it an encapsulation of the contrast both between and within the two movements of the symphony.
A work from the early 20th century, the Fifth Symphony is regarded as a modernistic musical piece. The symphony draws on all of the "deformation procedures" suggested by James Hepokoski regarding musical modernism: breakthrough deformation, introduction-coda frame, episodes within developmental space, various strophic/sonata hybrids and multi-movement forms in a single movement. Its fragmented nature,unpredictable character and sudden synchronization at the ending also point towards a self-conscious modernist aesthetic, though as in most of Nielsen's early and middle works, non-modernist devices, including organicism and diatonicism, play some essential roles.

Conductor: Herbert Blomstedt & San Francisco Symphony Orchestra