The bells were ringing in the dale
And men looked up with faces pale
The dragon's ire, more fierce than fire
Laid low their towers and houses frail
The mountain smoked beneath the moon
The dwarves, they heard the tramp of doom
They fled the hall to dying fall
Beneath his feet, beneath the moon
Far over the Misty Mountains grim
To dungeons deep and caverns dim
We must away, ere break of day
To win our harps and gold from him!
The wind was on the withered heath
But in the forest stirred no leaf
There shadows lay be night or day
And dark things silent crept beneath
The alliteration of “w” in this line creates the sounds of the wind on the heath. It also evokes the use of alliteration used in Old English poetry. For example in the poem,  The Seafarer , the alliteration of the “w” sounds likewise create the feeling of the desolation and isolation that is felt in this line by Tolkein. 
 
 iscealdne sæ winter wunade wræccan lastum, winemægum bidroren, 
 on the ice-cold sea dwelt for a winter in the paths of exile, bereft of friendly kinsmen, 
 
 ( The Seafarer , lines 13-16) 
 Source:  Anglo-Saxons.net