“From harmony, from heavenly harmony, This universal frame began […] The spheres began to move”: References to “musica universalis” (also called “music of the spheres”), a theory developed by the Greek philosopher Pythagoras arguing that the universe consists of celestial bodies whose movements produce inaudible, yet harmonious, “music.”
“nature underneath a heap / Of jarring atoms lay”: A reference to the Greek philosopher Epicurus and his theory that the world is made up of indivisible atoms.
“cold, and hot, and moist, and dry”: A reference to the atomic theory of Greek philosopher Aristotle, who argued that there are four sensible qualities to matter (hot, cold, wet, dry).
“When Jubal struck the chorded shell”: A Biblical allusion to Jubal, a character in the book of Genesis. Jubal was a descendant of Cain, the first musician in the Bible, and the “ancestor of all who played the harp and flute.”
“Orpheus could lead the savage race”: An allusion to the Greek mythological figure Orpheus, a poet and musician who was able to use his music to charm people, animals, and inanimate objects.
“But bright Cecilia rais'd the wonder higher: / When to her organ vocal breath was given […]”: A reference to St. Cecilia, a Catholic martyr and organ player from the 2nd or 3rd century A.D., commemorated as the patroness of musicians.