Say a composer read a poem. The poem is the published work of a living poet and obviously protected by copyright. This composer was inspired by the poem, and down the road he has written a piece of music that is his own artistic response to it.
The musical piece composed has no text (it is an instrumental work only), and any connections to the poem that inspired it exist solely in the composer's imagination.
At this point, is the composer's work derivative of the poem?
And if the composer indicates in program notes, discussion with the performers, an interview, etc. that it was inspired by that specific poem, does that then make it a derivative work?
And I'm assuming that were the composer to desire titling his work with the same title as the poem, that would definitely be derivative, and require permission?