Find a poem, or part of a poem which inspires you.
Particular images or moods may overwhelmingly capture the attention of the group. There may be a refrain in the poem which repeats, suggesting a musical theme to be repeated alongside the refrain each time.
You may select a reader of the poem who will pause at particular times for the music to "paint the picture" of the poem before the reader resumes. Sometimes, the music may belong mostly at the beginning to "set the stage" for the poem ahead of time, or the music may be what follows the reading of the poem. Or perhaps the poem is only read silently by the musicians, not aloud, and the music is a reaction to or representation of the poem.