Heard melodies are sweet, but those unheard Are sweeter; therefore, ye soft pipes, play on; Not to the sensual ear, but, more endeared, Pipe to the spirit ditties of no tone.

-Keats,John
  Lamia, Isabella, The Eve of St.  Agnes and Other Poems,'Ode on a Grecian Urn', stanza 2.

Make me thy lyre, even as the forest is: What if my leaves are falling like its own! The tumult of thy mighty harmonies Will take from both a deep, autumnal tone, Sweet though in sadness.

-Shelley, Percy Bysshe
  'Ode to theWestWind', l.57^61.