Their chaste-eyed Queen = Diana.
Brown exercise. Exercise is here personified and represented as brown and sunburnt.
Viol. A stringed musical instrument.
In Tempe's vale. In Thessaly, especially connected with the worship of Apollo, the god of poetry and music.
Sphere-descended maid. A metaphor common with the poets, and taken from a Greek fancy most elaborately described in Plato's 'Republic,' where the system of the universe is pictured as a series of whorls linked in harmony.
Thy mimic soul. Thy soul apt to imitate.
Devote = devoted. A form more close to that of the Latin participle, from which it is derived.
Thy recording Sister = the Muse of History.
Cecilia's mingled world of sound = the organ. So St. Cecilia is called in Dryden's Ode, "Inventress of the vocal frame."
The just designs = the well-conceived, artistic designs.]