A symphonic poem or tone poem is a piece of orchestral music which has a story attached to it or describes something such as poem or a painting or any idea which is not music. A symphonic poem is a kind of programme music (music for instruments which has an idea outside music).
Symphonic poems were mostly written in the 19th century at the time known as the Romantic period. They are normally in one movement lasting perhaps between 10 and 20 minutes. Some of the longest ones, such as Ein Heldenleben by Richard Strauss are much longer, like a symphony with four movements which run into one another.
The idea can be seen in Beethoven’s overtures which tell the story of the opera or play which is about to be performed. Composers such as Felix Mendelssohn then started to write overtures which told a story but were not attached to any opera. Fingal's Cave (1832) describes the sea lapping against the rocks of a cave in the Scottish Hebrides.
Franz Liszt was the composer who made the symphonic poem an important musical form. He wrote twelve works which he called Symphonische Dichtung (Symphonic poem) because the music developed in the same way as in a symphony. One example is Mazeppa (1851) which describes the poem by Victor Hugo about a wild horse that carries a man tied to him until he is rescued by the Ukrainians and made into their chief.
Other composers who wrote symphonic poems include Sergei Rachmaninoff, Modest Mussorgsky, Camille Saint-Saëns, Claude Debussy, Jean Sibelius, Bedřich Smetana, Antonín Dvořák, Pyotr Tchaikovsky and César Franck.