How does the speaker compare the girl’s voice to the natural sounds?

In William Wordsworth’s (1770-1850) poem “The Solitary Reaper” (1807), the poet travels through the Highlands of Scotland with his sister Dorothy. He sees a Highland girl alone in a field. She is cutting grain and singing a sad, sweet song. Her voice fills the quiet valley. The poet listens silently and feels peace in his heart. To show the beauty of her song, he compares it with the two sweetest sounds in nature: the nightingale and the cuckoo bird.

The Nightingale’s Song: The poet first compares the girl’s song to that of the nightingale. The poet says her song is sweeter than that of the nightingale. He says,

“No Nightingale did ever chaunt 

More welcome notes to weary bands.”