My point is that we don't really know what we are talking about when we are talking about musicality in poetry. I propose this as an analytic beginning:
We can talk about it literally, in terms of the sound and rhythms of poetry, and its direct connection to music in genres of sung poetry / vocal music.
Music is also one of the main metaphorical systems for talking about poetry. But on closer examination it is never merely a metaphor (except in merely conventional references!) because of these literal connections. What I call "deep musicality" is that connection between the central metaphor and the physical embodiment.
My assumption is that we know a lot about this, but we don't know exactly what it is that we do know, so we have to write down what we know and see where we are at. I'm not sure yet whether there are four or twelve kinds of things that people mean when they talk about poetry as "musical."