Answer:
The line "Each singing what belongs to her, and to none else" is best paraphrased by the sentence Every job is unique and valuable to America.
Explanation:
Walt Withman celebrated individuality in his work, he considered that those differences from one another were the ones who made us special, unique and valuable, in this piece of work he makes metaphors comparing the actions of American workers with musical sound and how they all with their very individual abilities and jobs create the general orchestra which could not be done without any of them, that's what matters that what makes them count.