aka "Down in Those Valleys Below". Traditional Cornish folk song [Roud 371; Ballad Index K089; VWML SBG/1/1/90; Wiltshire 990, 991; trad.] dating back to the 1600's. The words were first published in Robert Bell's Ancient Poems of the Peasantry of England, 1857.
My sweetheart, come along, don't you hear the fond song, The sweet notes of the nightingale flow? Don't you hear the fond tale of the sweet nightingale As she sings in the valley below.