The Baroque music era introduced and popularized purely instrumental composition, music for its own sake; non-representational, mathematically based exercises, essentially. But through the Baroque, many examples of what could be called program music were written, notably Handel's Water Music and Music for the Royal Fireworks, or Vivaldi's Four Seasons which used the vocabulary of the smaller Baroque orchestra to illustrate the aspects like rain, budding growth, or chilly winds of the four seasons of the year.
Program music can invoke in the listener a specific experience other than sitting in front of a musician or musicians. It is in this way related to the purely Romantic idea of the Gesamtkunstwerk describing Wagner's Operas as a fusion of many arts (set design, choreography, poetry and so on), although it relies solely on musical aspects to illustrate a multi-faceted artistic concept such as a poem or a painting. The dynamics of sound that were newly possible in the Romantic orchestra allowed composers of the era to focus on emotions and abstract, intangible aspects of life much more than during the Baroque or Classical music eras.
Symphony No. 3 and Symphony No. 6 of Beethoven, who is considered the first Romantic composer, illustrate the intangible concepts of heroism and "pastoral" nature respectively. Hector Berlioz's Symphonie Fantastique was a musical narration of a hyperbolically emotional love story he wrote himself. In 1875, Modest Mussorgsky composed using only the dynamic range of one piano a series of pieces describing seeing a gallery of ten of his friend's paintings and drawings in his Pictures at an Exhibition, which was later fully orchestrated by Maurice Ravel to bring more depth to the musical metaphors.
Single movement orchestral pieces of program music are often called symphonic poems.