Mackey in Cork, Ireland, 2005. Courtesy of the authorIn an era when poetry is increasingly compressed to fit our iPhone screens, Nathaniel Mackey has been writing two astonishing long poems—“Mu” and Song of the Andoumboulou—across multiple books for the past thirty-five years. “Mu” and Song of the Andoumboulou are two ongoing sequences beaded with his insights on cosmology, grief, ancestry, migration, and black life. The utterance mu suggests “mouth,” “myth,” but also “muse,” whereas Mackey …