Question

what would the tone of walt whitman's poem "I hear America singing" be if the people in the poem were speaking rather than singing?

Answer 1

The correct answer is "less hopeful". 
This is because all the characters in the poem sing as they are doing their work, thus creating the identity of a happy America where the workers enjoy and sing. 
If they weren't singing, they would be presented as people with no hope who are doomed to work day in day out for the elite. 
This is not something that Whitman supported as he wanted to present America as a joyous place.