Question

What was the guesses the poet makes with the regard to the solitary reaper's song?

Answer 1

it is a melodious song and singing with sad

Answer 2

The poet was not able to understand the lyrics of the solitary reaper's song but, he could analyse from the tone of the song that she was singing a melancholy strain. Thus, he made several guesses about what she was singing ,like he guessed that it could be an ordinary song, familiar to day to day affairs or she was singing about some natural sorrow, loss or pain, that had occured or may be again.