Answer and Explanation:
Walt Whitman was an American poet who lived from 1819 to 1892. He is, to this day, considered to be one of the greatest writers in America. In his poem "I Hear America Singing", the working class is singing a song. Each one - the mechanic, the seamstress, the mason, the carpenter - sings a unique song, a song of their own individuality.
Those of mechanics, each one singing his as it should be blithe and strong,
The carpenter singing his as he measures his plank or beam,
The mason singing his as he makes ready for work, or leaves off work,
[...]
Each singing what belongs to him or her and to none else,
However, it is this uniqueness that constitutes America, that contributes to make it the great country it is. No wonder Whitman makes a point of repeating the term "singing" throughout the poem. He is describing a symphony of voices, hearts, dreams, and ideals. Each person sings of his or her own life, happiness, strength.