There are several literary devices being used.
Imagery - High above us in the darkness
Personification - A solitary mocker poured out his repertoire
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This sentence contains imagery, as it vividly describes the scene using sensory details. It also includes personification since it attributes human-like qualities to the bird ("blissful unawareness"). Additionally, it features metaphorical language as it compares the bird's singing to a "repertoire."