What theme is emphasized in this excerpt from "ode on a grecian urn" by john keats? heard melodies are sweet, but those unheard are sweeter; therefore, ye soft pipes, play on; not to the sensual ear, but, more endear'd, pipe to the spirit ditties of no tone: fair youth, beneath the trees, thou canst not leave thy song, nor ever can those trees be bare; bold lover, never, never canst thou kiss, though winning near the goal yet, do not grieve; she cannot fade, though thou hast not thy bliss, for ever wilt thou love, and she be fair!