The poem begins with the speaker declaring, in the first person, that he or she hears "America" itself singing. But, in the second half of the line, the speaker notes that the song America sings is actually many separate songs—"varied carols." The word "carols" is especially intriguing in this context, since it is often used for religious songs—and this is very much not a religious poem! The word suggests that Americans dedicate themselves to their country and their work with a passion and devotion that approaches religious faith.
The speaker then moves on to note some specific "songs" being heard: those of mechanics, carpenters, and masons. The speaker will follow this pattern throughout the rest of the poem, celebrating working Americans whose lives are humble and whose work is often difficult and physical. The fact that their songs are "blithe," meaning cheerful, and "strong" underscores the speaker's broader vision of America as a place where people find joy and fulfillment in their work. And as the poem describes these people, the speaker notably avoids using much fancy, literary language. Instead, the poem's tone is casual and conversational.
While it’s certainly possible that all these mechanics, carpenters, and masons are literally singing to pass the hours, it seems more likely that this "singing" is a metaphor. On the one hand, it represents the pride and joy Americans take in their work. It also is meant to reflect the way America as a united nation emerges from its individual citizens, their unique songs blending into a broader harmony, so that, as the speaker says in the poem’s first line, "America" itself is "singing."
As the poem celebrates the diversity and richness of American life, it also tries to find a distinctly American music. Whitman rejects European poetic traditions like meter and rhyme, which feel too constraining to capture the energy of American life. Instead, the poem is written entirely in free verse, and Whitman turns to other devices to make his poem sound musical.
The most obvious of these devices is anaphora, in the repeated phrase, "I hear [insert professional] singing," which begins in line 3. This anaphora operates a little bit like meter: it creates a sense of expectation in the reader, and it separates the poems long lines into more manageable chunks.
The poem also turns to other devices to guide the reader through its long lines and to make its simple language feel poetic. For example, almost all of the lines in the poem are end-stopped. This helps give the lines a sense of definition and integrity even as they expand and contract unpredictably. Further, the speaker uses devices like chiasmus to make the poem feel musical without rhyme. Line 1, for instance, can be divided into two halves, separated by a caesura; in the second half of the line the speaker repeats the information that was provided in the first half, but in reverse order, creating an ABBA pattern:
I hear America singing, the varied carols I hear,
In this line: "I hear" repeats at the beginning and end, while "America singing" and "varied carols" are just different ways to refer to the same thing: the various songs of American workers.
Similarly, the poem is dense with assonance. Line 4 contains, for instance, contains repetition of the long /a/ sound, the short /i/ sound, the long /ee/ sound, and two variations of the /o/ sound:
The mason singing his as he makes ready for work, or leaves off work,
The poem is thus not only about America singing: it makes itself into an example of a distinctly American music.