musk rose, n. - An autumn-flowering, climbing garden rose, Rosa moschata (not known for certain to exist in the wild), with large white musk-scented flowers growing in clusters. Also: any of certain hybrids evolved from this (more fully hybrid musk rose).

This entire stanza relies heavily on scent, as before his other senses are heightened by the lack of vision. The "musk-rose" is a strange flower, mostly because they are so common they can practically go unseen. It is only because of its strong scent it gains the attention of passersby or insects to pollinate. In the next like he can hear the flies which are attracted to the musk of the flower.

"musk rose, n." OED Online. Oxford University Press, September 2015. Web. 6 December 2015.

Not real incense, just the strong scents of nature. He cannot see what he is smelling in the darkness, making his sense of smell all the more keen.

I wonder if scent/smell is a feminized sense...