Adaptation?

Rorem makes the point that a song are not adaptation of a poem, because the poem is still there, intact. He says this is the only kind of union of two artistic media that works in this way. For example, if we adapt a novel into a movie, the novel disappears.

I would say that there are other cases, like if we were to put choreography to a piece of music: the music is still there, right? But his point is still a valid one. The translation replaces a text with another; the song setting does not.