Reading the title, the reader may expect the poem to be set in the country, because a reaper generally works in the fields.
One interesting element that draws the attention of the reader, is the use of the adjective "solitary"; this choice evokes a melancholy atmosphere.
There is a third person narrator, that invites the passer-by to look at a girl while she is reaping and singing a melancholic song that seems to fill the valley with an echo effect. Her voice is so beautiful that, according to the poet, is better than nightingale's voice.
But what's that song about? Here, the poet, makes hypothesis to understand what the girl is singing; maybe a historical song. However, the poet is charmed by the notes of the song.
Analysing the connotative level, the poem is divided into four octaves. In the first stanza, he describes the lonely girl working and the landscape, using imperative too (to make understand the reader not to disturb the song of the lady) and melancholic notes. Sounds are soft to give idea of an open space. The first two stanzas, represent a descriptive part and so the rhythm is slow, just to evoke the sensation and the beauty of the strain.
On the other hand, the second part of the poem, is a reflective part, because the poet makes some hypothesis: we are able to understand that it's a reflective part because there are some rethorical questions. Moreover here the rhythm is faster because of some run on lines too.
The last part of the poem is characterized by a slow rhythm again, because the poet is motionless, and he tries to capture the music's song into his heart.
Another last important thing: expressions like sing, sound, voice, hear, evidence a semantic field: the hearing sense.

Marco Cozzutti 5B