“Heard melodies are sweet, but those unheard / Are sweeter”: Keats’s famous lines remind us that the idea of an unheard music somehow inside the poem is central in romantic poetry. Their familiarity shouldn’t keep us from noting the basic strangeness of the image: an unheard melody is a contradiction in terms. The phrase refers to a remembered or imagined and therefore silent music: “ditties of no tone” can’t be perceived by “the sensual ear,” only by the mind or spirit. That Keats is contemplating painted figures on an ancient Greek urn fits nicely with Jackson’s point about the Alexandrian songbook. Lyric poetry positions itself in the ode as commentary on an ideal music that belongs to the remote past. But we might say something similar about poetry’s relation to the exquisite birdsong in “Ode to a Nightingale,” which is just as tantalizingly elusive (“Fled is that music . . .”). The distance between lyric poetry and music is not simply a fact of historical belatedness with respect to the supposed pre-textual unity of sign and sound in sacred ritual and ceremony. Nor is it a product of the evolutionary differentiation of the sister arts. It is a seemingly perennial figure by means of which lyric texts imagine what they are and do.

Or perhaps there may be a still more fundamental allegory implied in the structure of these poems, the story of how reason and reference arise from, and then ride on top of, non-rational and non-referential linguistic structures—structures which, insofar as they are acoustic, can be thought of as a music that precedes speech and is always available as the material basis for new speech.