This poem was written to celebrate St. Cecilia (the patron saint of music) and argues that the heavens (God) lent order and harmony to the jarring, chaotic universe of nature. The universe, in Dryden's speaker’s understanding, is not random, chaotic, or confused. On the contrary, he states that God's presence puts all the elements in the universe in their proper place so that they all work together harmoniously. The narrator uses the metaphor of music to describe this beautiful harmony, likening the God-controlled universe to music. The grand culmination (or final swelling chord: i.e. "diapason") of this harmony is none other than "man."

Dryden’s speaker argues that this music does not simply bring a passionless order and harmony. It raises emotions and subsequently "quells" or soothes them. It elicits an awe in us and a desire to worship a God who created such beautiful harmony. It proves to people that nothing other than "a god" could live at the center of such a universe. The speaker uses the metaphor of a conch shell to describe the universe, with God at its center. Therefore, one theme of the poem is that we live in a universe that is ordered, harmonious, and awe-filled because of God's control.

One theme in the poem is that humankind is the grand culmination of this celestial harmony. If the music that humans create is ordered and harmonious (no matter the instrument), it is therefore an implicit reflection of God's ordered and harmonious nature. This includes the music of poetry, such as the ordered and harmonious poetry that Dryden composes. Dryden’s speaker explicitly states that the best reflection of God's harmony is inherent in the music of St. Cecilia; her music was so heavenly that an angel heard it and mistook Earth for heaven. Thus, the poem implies that humankind can (at least in rare moments) reach heavenly or divine heights on Earth. Dryden’s work, therefore, posits a very positive and optimistic view of humankind, an outlook rooted in Enlightenment ideals. This Enlightenment viewpoint is also firmly entrenched in a Christian worldview. The poem, in the final chorus, ends by invoking the Second Coming and the New Jerusalem, when all the "dead shall live, the living die" and all are united in universal harmony. Like an uplifting piece of music, the Christian universe described is based on a plan with a beautiful ending.

Throughout the poem, Dryden’s speaker emphasizes the various ways that music is impactful. Music is celestial and connected to God, according to the poem, yet it also is not perfectly happy. What makes music perfect seems to be its ability to capture a wide array of human emotions and experiences. For example, music can capture a triumphant spirit that calls soldiers into battle. Its impact, then, is one that is jarring and thundering; it is designed to get its listeners on their feet. On the other hand, music has the ability to convey the “woes” of lovers who have been separated or hurt. Their loss is expressed by the sad tones of the flute. So, too, can violins make sharp and piercing responses to jealousy, desperation, and pain. In summary, music can do much more than call us to the heavens or remind us of our greater purpose. Music can describe and enhance human experiences—it might even help us make sense of these emotions.