The quirk which inheres in John Keats' prosody- that it is a kind of representation or enactment of ecstatic states of consciousness, or euphoria- is balanced, in some of the Odes, especially Nightingale and Grecian Urn, by the appearance, within the consciousness of the protagonist, of the second meaning of "ecstasy" in the nineteenth century or back- the circumstance by which a person transcends their own skin, into dementia or madness, past the limitations of the physical. That's why the magnificence of Keats' prosody, its euphoric "ecstasy," can work for or against the narrative-thematic gist of what is being imparted, especially when the other, foreboding side of "ecstasy" is being investigated. Here, the prosodic heft of Keats' language has a phallic quality of triumphant euphoria:
What leaf-fringed legend haunts about thy shape
Of deities or mortals, or of both,
In Tempe or the dales of Arcady?
What men or gods are these? What maidens loth?
What mad pursuit? What struggle to escape?
What pipes and timbrels? What wild ecstasy?
But in Nightingale, the two strains of ecstasy chafe against each other in such a way that "ecstasy" and its doppelganger are at loggerheads. Why this is interesting is that once Keats' prosodic superiority to the entire English-language canon is established, we may start to look at his music and how it functions within itself, both in relation to narrative-thematic elements and in relation to the structural semantic and syntactic elements which configure it as a self-sufficient linguistic system.