The repetition of singing throughout the poem paints a picture of many Americans working and singing at the same time. The poem also repeats the idea that each person's song is his own, so the image is one of many different songs being sung at once. Their songs and jobs are all different, but they seem happy and joined together in song
Even mature plants sag in the direction of the brightest light. They accomplish this by lengthening the stem cells on the side that is farthest from the light. Phototropism is the name for this form of light-oriented development.