A symphonic poem or tone poem is a piece of orchestral music in one movement in which some extra-musical programme provides a narrative or illustrative element. This programme could come from a poem, a novel, a painting or some other source. Music based on extra-musical sources is often known as programme music, while music which has no other associations is known as abstract music.
Franz Liszt largely invented the symphonic poem, in a series of single-movement orchestral works composed in the 1840s and 1850s. The immediate predecessors of Liszt's tone poem were concert overtures, theatrical, colorful and evocative orchestral movements that were created for performance independent of any opera or theater-piece: for example, Mendelssohn's Fingal's Cave or Hector Berlioz' Roman Carnival Overture. These in turn sprung from the overtures by Ludwig van Beethoven such as those for Egmont, Coriolan, and the Leonore No. 3, which in their musical content anticipate the story of the stage work which they introduce (plays in the case of Egmond and Coriolan, the opera Fidelio in the case of Leonore). Even earlier orchestral mood pieces are exemplified by the 'storm' set-pieces that were an established genre that went back to the summer storm in Vivaldi's Four Seasons, and some moody entr'actes between scenes of Baroque French operas.
Other composers took up the symphonic poem: Smetana (Ma Vlast), Dvorák (with pieces such as The Golden Spinning Wheel and The Wood Dove), Mussorgsky (Night on Bald Mountain), Tchaikovsky, César Franck's Le Chasseur Maudit ('The Accursed Huntsman'), Paul Dukas (L'apprenti-sorcier), Ottorino Respighi (the trilogy of Roman symphonic poems The Pines of Rome, The Fountains of Rome and Roman Festivals), and many less well-known composers, such as Bax with Tintagel, and The Garden of Fand..
Richard Strauss (who preferred the term tone poem to symphonic poem) was one of the most prolific late Romantic composers in the genre, with his works including Don Juan, Til Eulenspiegel, Also sprach Zarathustra and Don Quixote. Strauss subtitled Don Quixote 'Introduction, Theme with Variations, and Finale' and 'Fantastic Variations for Large Orchestra on a Theme of Knightly Character.' The work could as easily be called a rhapsody (q.v.) as a tone poem.
There are also a number of one-movement works not written for orchestra, but for some chamber ensemble or solo instrument, based on some extra-musical source. Because of their non-orchestral nature, these are not considered to be "symphonic poems", although in all aspects other than instrumentation, they resemble one. One of the best known such pieces is Arnold Schoenberg's Verklaerte Nacht, based on a poem, originally written for string sextet (though later arranged for a larger ensemble).