Autumn Refrain by Wallace Stevens   What do we mean when we say that a poem is “musical”? Of course, there are many answers posited to this question, most having to do with traditional formal devices like rhyme and iambic pentameter, or with the ancient kinship between song and lyric poem. Yet the simplest definition of form or structure, and therefore of the potential patterning of music, is that some element varyingly repeats itself, and this repetition may apply on any scale, from the smallest unit of the letter to whole lines or stanzas of refrain. In free verse, which, for better or worse, has become the normative practice of our time, our ears are poised to register variations in rhythm or tonality. (Louise…