The composer who developed the symphonic poem was

The developer and the first known with the term symphonic poem was the composer Franz Liszt.

Explanation:

Symphonic Poems are a series of thirteen orchestral works that are numbered as S.95-107. The first twelve were composed in ten years, although part of the material used was previously devised.

Liszt wrote prefaces for nine of his poems. However, the vision he had of the symphonic poem tended to be evocative, using music to create a general mood or atmosphere instead of illustrating a narrative or describing something literally.