Question

read the excerpt from \the weary blues.\
he made that poor piano moan with melody.
o blues!
swaying to and fro on his rickety stool
he played that sad raggy tune like a musical fool.
sweet blues!
coming from a black mans soul.
o blues!

the phrases \o blues!\ and \sweet blues!\ are examples of

alliteration.
repetition.
hyperbole.
simile.

Explanation:

Alliteration is the repetition of initial consonant sounds, which is not the case here. Hyperbole is extreme exaggeration, and simile uses "like" or "as" to compare two things, neither of which match these phrases. The phrases "O Blues!" and "Sweet Blues!" repeat the core term "Blues!" with slight modifiers, fitting the definition of repetition, where words or phrases are reused for emphasis or rhythm.

Answer:

repetition.