But here there is no light,
Save what from heaven is with the breezes blown
Through verdurous glooms and winding mossy ways.
I cannot see what flowers are at my feet,
Nor what soft incense hangs upon the boughs,
But, in embalmed darkness, guess each sweet
Wherewith the seasonable month endows
The grass, the thicket, and the fruit-tree wild;
White hawthorn, and the pastoral eglantine;
Fast fading violets cover'd up in leaves;
And mid-May's eldest child,
The coming musk-rose, full of dewy wine,
The murmurous haunt of flies on summer eves.
Darkling I listen; and, for many a time
I have been half in love with easeful Death,
Call'd him soft names in many a mused rhyme,
The adjective ‘murmurous’ is internally  alliterative  with its repeated, soft ’m’s and buzzing, sibilant ’s'. 
 The line contrasts with the rest of the stanza, where nature is praised, described as ‘sweet’, and  the scent of musk-roses compared to wine.