It is the vowelling of a line, far more than the bundling of the consonants that makes it sound good or bad. A thousand things have to be considered in poetry. There is the requirement that the line should be a pleasant variation from its predecessor; that the syntax should fit naturally into the space to be filled; that the stresses of the line should support the meaning; and when all these requirements are fulfilled it would be worth considering whether certain consonants or clusters of sounds which are thought cacophonous may be rearranged . . . The Anglo-Saxons seem unaware of this cacophony, yet they pay very careful attention to vowelling and many of their lines are heavily sonorous.
—Charles Williams
Unknowing 