Symphonic Poem and Programmatic Symphony

Two typical forms of orchestral program music in the Romantic era were the programmatic symphony and the symphonic poem.  The structural elements of the programmatic symphony were largely free of Classic predictability.  Its programmatic content could vary from a simple extramusical title to an elaborate verbal description.

The symphonic poem was the invention of Franz Liszt and was sometimes called a Tone Poem, especially when it was based on a poetic idea.  The form comprises one continuous movement and is usually based on the principle of variations on a theme, or contrasting themes, that are inspired by a program or a literary idea.  It is a transformation of themes in which they retain their identity through various stages and forms.

(See the article:  The Symphonic Poem)