This quote is a beautiful and profound comparison between the mundane and the divine, the earthly and the celestial. The "squeaking of the pump" refers to a commonplace, earthly sound, the kind of noise one might hear in everyday life. It’s not particularly pleasant or musical, but it’s a necessary part of life. On the other hand, the "music of the spheres" is a concept from ancient philosophy, referring to the harmonious sound that the celestial bodies (planets, stars, etc.) are believed to produce as they move in the universe. This sound is divine, celestial, and perfect.

Thoreau is saying that both these sounds, as different as they are, are equally necessary. The mundane and the divine, the earthly and the celestial, are both essential parts of existence. We need the squeaking of the pump just as much as we need the music of the spheres. This is a call to appreciate all aspects of life, from the most humble to the most exalted.

In today’s world, this quote can be a reminder to value all experiences, both the mundane and the extraordinary. In the hustle and bustle of modern life, we often seek extraordinary experiences, forgetting to appreciate the ordinary moments. But these ordinary moments, like the squeaking of the pump, are just as necessary and valuable as the extraordinary ones.

In terms of personal development, this quote can remind us to find value and meaning in all experiences, even the ones that may seem mundane or unpleasant. Every experience, every moment, has something to teach us. The squeaking of the pump can be just as instructive, just as necessary for our growth, as the music of the spheres.