There are several literary devices at work in the first line of Langston Hughes' poem “The Weary Blues.”
Like most of Hughes' work, this poem isn't trying to be difficult to understand. Hughes usually comes right at his reader, creating a mood that envelopes his everyday message. That's why Hughes works so well at the high school level, it's great poetry but you don't need a masters degree to know what he's writing about.
“The Weary Blues” is about piano-playing bluesman who, like most blues artists, has a heavy heart. Hughes starts the poem with the lines
Droning a drowsy syncopated tune,
Rocking back and forth to a mellow croon,
I heard a negro play.
Poetry isn't only about the meaning of the words we read, it is also about sound of the words we read. In the line “Droning a drowsy syncopated tune” Hughes is employing three different sound devices.
The first and easiest to discern is the alliteration created by the repetition of initial “d” sounds in “droning” and “drowsy.” He also uses assonance, which is the repetition of vowel sounds, with the “oh” and “ow” sounds in “droning,” “drowsy,” and “syncopated.” Finally, he creates consonance, the repetition of consonant sounds, with “syncopated tune.” The repeated consonant sounds in these two words are the “sy” (sounds like “see”) “p,” and “t.” Notice that the “t” sound appears twice.
If you aren't familiar with consonance, you may wonder how it differs from alliteration. Consonance is the repetition of consonant sounds anywhere in a short space, not only at the beginning of words, as with alliteration.
The first line of the poem also establishes thematic diction (word choice) with the word “droning.” Hughes is going to use several words to describe how sounds are made in a blues song. Later in the poem we also get the words “croon,” "crooned," and “moaning.” This word choice helps establish the idea that the blues is a mournful musical genre.