Final answer:
Liszt developed the symphonic poem, a single-movement orchestral piece that evokes a non-musical source, contributing to the Romantic movement's evolution of classical music.
Step-by-step explanation:
Liszt developed a new symphonic form called the symphonic poem. This form attempted to create a single-movement piece of orchestral music that illustrates or evokes the content of a poem, story, novel, painting, landscape, or other (non-musical) source. The innovation was one of several responses to the larger Romantic movement where composers like Berlioz, Strauss, and Wagner were also pushing the boundaries, challenging audiences, and contributing to the evolution of classical music traditions. The symphonic poem differs notably from the typical multi-movement symphony format that had been established by earlier Classical composers such as Haydn, Mozart, and Beethoven.