Walt Whitman has been called the father of the free verse. What effect does this poetic form have in the poem overall

Although Whitman is describing actual songs in this poem, there are instances earlier in the collection where he uses the word "sing" to stand in for "write" when referring to his poetry. This is because of Whitman's belief that poetry was strongest as an oral medium. Whitman wanted his poems to be spoken aloud because the words became more powerful when they can transcend the page. Because of this strong connection between music and poetry, Whitman often wrote his poems in a way that mimicked the natural rhythms of recitation and music.