Each stanza in this poem begins with the command, "Beat! beat! drums!—blow! bugles! blow!" The speaker commands the instruments to play so loudly that the sound bursts through the windows and doors of various places. He imagines the sound filling the church, causing the congregation to scatter, interrupting a scholar studying at school, disturbing a bride and groom trying to get some privacy, and finally, the farmer who is hard at work in his field. He describes the sound cutting through the loud traffic in large cities, keeping people awake, and drowning out the sounds of shoppers, singers, and conversations, even disturbing a lawyer during trial. He encourages the instruments to continue playing, despite any objections from people weeping or praying, and to play so loud that they even "shake the dead."
This poem is made up of three stanzas with seven lines each. Whitman wrote "Beat! Beat! Drums!" in free verse, like most of his poems. He does repeat the same line ("Beat! beat! drums!—blow! bugles! blow!") at the beginning of every stanza, which gives it some order. The rhythmic pulse of this line underlines the poem's content. The short, repeated syllables mimic the sound of drums beating and bugles blowing. Only the final line of each stanza falls into a specific meter; in this case, it's iambic heptameter, which adds to the pulsing, drum-like rhythm of the poem.
Whitman wrote this poem at the beginning of the Civil War. Whitman uses the drums and bugles as symbols of the war itself (during the wars of early American history, drums and bugles would signal the beginning of each battle). In this poem, the speaker commands the instruments to play so loudly that they disrupt everyone's lives, just like war changes a society. This was especially true of the Civil War, as all the soldiers were American and all the battles took place on American soil. The war dictated everything that happened during period of American history. In this poem, Whitman does not let his reader escape the incessant drumbeat and trumpeting bugles, just as there was no escaping the Civil War.
As is common throughout the poems in Leaves of Grass, Whitman uses lists in "Beat! Beat! Drums!" Throughout the poem, the speaker lists the places he wants the music to reach (the church, the school, the city full of traffic, the houses, the courtroom) and the people he wants it to affect (brokers, singers, lawyers, farmers). Though he could have merely spoken about one or two of these, the use of the list really drives home the major theme of this poem: war affects everyone and everything. Whitman invokes the environment of war without once mentioning soldiers. Instead, Whitman draws focus to those that history ignores - the everyday Americans to whom many of his readers can relate.
Whitman employs onomatopoeia when he writes about these instruments, using words like whirr, pound, and thump. He draws the reader into his world, so while we read about the instruments playing, it is possible to hear them as well. It adds an additional experiential dimension to the poem. The onomatopoetic diction becomes increasingly intense towards the end of the poem, as if the sounds of war are getting louder as they grow closer and more dangerous.
The end of the poem is rather macabre because the speaker commands the music to be so loud that it even wakes the dead. While the horns and bugles signal the beginning of the battle, and the mention of the dead invokes images of war cemeteries with rows upon rows of graves - the end result of the battles. Just as Whitman uses onomatopoeia to allow readers to hear the sounds of war, he also makes the reading experience visual with these potent images of death.