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 man's soul.
o blues!

the phrases “o blues! ” and “sweet blues! ” are examples of
alliteration.
repetition.
hyperbole.
simile.

B) Repetition.

Explanation: Repetition is a literary device that consists in repeating a word or phrase in a text to emphasize on an idea or a meaning. It is often used as a rhetorical device to add more power to certain words or sentences. In the given lines, we can see a clear example of repetition, in the phrases "O Blues", "Sweet Blues" and then again "O Blues" which helps to emphasize in this phrases and also create rhythm in the text.

his tongue, i believe, was bloody and hanging out of his mouth.

he looked as if he were hungry.

he has several wolf-like qualities; a gray coat, sharp claws and yellow fangs.

those eyes made me feel, dear reader, like the end was near.

as i reached for a stick, he moved to the other side of the hill.

panting and hungry, he looked at me, a defenseless human and he snarled.

well i said my prayers, however, he simply turned and limped off.