conuly

The splendor falls on castle walls
And snowy summits old in story;
The long light shakes across the lakes,
And the wild cataract leaps in glory.
Blow, bugle, blow, set the wild echoes flying,
Blow, bugle; answer, echoes, dying, dying, dying.

O, hark, O, hear! how thin and clear,
And thinner, clearer, farther going!
O, sweet and far from cliff and scar
The horns of Elfland faintly blowing!
Blow, let us hear the purple glens replying,
Blow, bugles; answer, echoes, dying, dying, dying.

O love, they die in yon rich sky,
They faint on hill or field or river;
Our echoes roll from soul to soul,
And grow forever and forever.
Blow, bugle, blow, set the wild echoes flying,
And answer, echoes, answer, dying, dying, dying.

https://poets.org/poem/splendor-falls

I heard a lovely musical arrangement of this once, but I've never been able to find it since. Other ones, but not the one I'm thinking of.