D.H. Lawrence, Poetry of the Present:
It seems when we hear a skylark singing as if sound were running forward into the future, running so fast and utterly without consideration, straight on into futurity. And when we hear a nightingale, we hear the pause and the rich, piercing rhythm of recollection, the perfect past. The lark may sound sad, but with the lovely lapsing sadness that is almost a swoon of hope. The nightingale’s triumph is a pæan, but a death-pæan.
So it is with poetry. Poetry is, as a rule, either the voice of the far future, exquisite and ethereal, or it is the voice of the past, rich, magnificent. When the Greeks heard the Iliad and the Odyssey, they heard their own past calling in their hearts, as men far inland sometimes hear the sea and fall weak with powerful, wonderful regret, nostalgia; or else their own future rippled its time-beats through their blood, as they followed the painful, glamorous progress of the Ithacan. This was Homer to the Greeks: their Past, splendid with battles won and death achieved, and their Future, the magic wandering of Ulysses through the unknown.
With us it is the same. Our birds sing on the horizons. They sing out of the blue, beyond us, or out of the quenched night. They sing at dawn and sunset. Only the poor, shrill, tame canaries whistle while we talk. The wild birds begin before we are awake, or as we drop into dimness, out of waking. Our poets sit by the gateways, some by the east, some by the west. As we arrive and as we go out our hearts surge with response. But whilst we are in the midst of life, we do not hear them.