Rhetorical Devices in Ode on a Grecian Urn
Brede is an interwoven pattern. Although Keats is using it literally to describe the art presented on the urn, notice how it also describes the tangled nature of the thoughts and philosophical questions the poem presents.
Keats establishes the urn as a character when he names it "Sylvan historian." Because the urn has been around so long and seen so many people come and go, its timelessness and resilience makes it an active part of history. "Sylvan historian" is a way of saying the urn is a mythical deity who has become wise from so many years on earth.
Meaning, not to the physical ear or to the one attached to the senses. Instead, the speaker refers to the ear of one's heart or mind, which responds to the "sound" of the pipes played in this scene as if they were, in fact, real.