This is a good point, but I took murbard2's post (https://news.ycombinator.com/item?id=9708591) to refer to works that are intended to be musical, but that can be recognised as poetry, rather than to works that were first written as poetry, and then set to music. (I recognise that I am on possibly dodgy grounds here by trying to determine whether a given work is 'really' poetry, but musical, or 'really' music, but poetic.)
