Sentence:  For sure the milder planets did combine / On thy auspicious horoscope to shine . . . / : And then, if ever, mortal ears / Had heard the <WSD>music of the spheres</WSD> 
Meaning of the word marked with <WSD> tags:  A continuous, glorious, harmonious set of sounds that are not audible to ordinary human beings, produced by the movement of the celestial bodies.