Which of the following is an example of program music?

Program music is a type of instrumental music that intends to evoke an extra-musical narrative or imagery, often telling a story or depicting a scene. It is characterized by its connection to a specific theme, poem, story, or scene outside of the music itself.

A symphonic poem is a prime example of program music, as it is a single-movement orchestral work that is often inspired by literature, painting, or a specific emotion or story. Its purpose is to convey a visual or emotional narrative through orchestral sound, making it a strong representation of programmatic content.

On the other hand, a sonata and a concerto are primarily structured forms of music that focus on the development of themes through instrumental techniques and do not inherently convey a specific narrative. Similarly, a ballade, while it can be descriptive in some contexts, generally refers to a particular form in music that may or may not convey a programmatic aspect. Therefore, the symphonic poem stands out as an unmistakable example of program music due to its intended focus on storytelling and imagery through instrumental means.