When I was meditating, I tried to perceive the universe as an immense symphony ... One day, I felt myself carried away in space, very far away, and suddenly I heard that the whole universe was singing ... no human music can compare to what I heard ... This music is not heard with the physical ears, but with the soul, with spirit ... This experience that I had so early in my life has remained like a seal in my soul and has pushed me to seek harmony always and everywhere.

Like how stars might sound. Or moons But not mountains. Too floaty for mountains. It's a sound like one planet singing to another, high stretched and full of different voices starting at different notes and sloping down to other different notes but all weaving together in a rope of sound that's sad but not sad and slow but not slow and all singing one word.
One word.

In this world, everything has a pulse or a vibration. This sound is unique to each living or non-living thing and in itself creates a music that no-one can hear. I believe that this has a very powerful resonance with, and a deep effect on, our lives. What would happen if we took this further and applied it to bigger things, more powerful things; like an entire solar system or galaxy say, what would that sound like?
Musica Universalis is the ancient theory that every celestial body, the sun, the moon and the stars, has an inner music. This is a harmonic and mathematical concept derived from the movements of the planets in the solar system. The music created is inaudible to the human ear.
Music of the Spheres is my interpretation of this theory. Every planet and every star; the whole universe has music within it that no-one can hear. This is what it would sound like if it was set free. This is Music of the Spheres. (from the introduction to Music of the Spheres)

i closed my eyes
to look inward
and found a universe
waiting to be explored

Words are flowing out like endless rain into a paper cup,
They slither wildly as they slip away across the universe
Pools of sorrow, waves of joy are drifting through my open mind,
Possessing and caressing me.
Images of broken light which dance before me like a million eyes,
They call me on and on across the universe,
Thoughts meander like a restless wind inside a letter box
They tumble blindly as they make their way
Across the universe
Sounds of laughter shades of love are
Ringing through my open ears inciting and inviting me
Limitless undying love which shines around me like a
Million suns, and calls me on and on
Across the universe

We do not realize the sound the world makes-unless of course, it comes to a stop. Then, when it starts, it sounds like an orchestra.
Breaking waves. Whipping wind. Falling rain. Squawking birds. All throughout the universe, time resumed and nature sang.

The only way you can talk about this great tide in which you’re a participant is as Schopenhauer did: the universe is a dream dreamed by a single dreamer where all the dream characters dream too.

There are so many elements flying in so many different directions that you really have to go with what feels like instinctively. The nature of the universe is fairly whimsical and nonsensical. In the most somber, beatific peacefulness there's complete chaos and maniacal laughter. I think music that doesn't reflect that is boring.

Hey, you!
Heaven!
Off with your hat!
I am coming! Not a sound. The universe sleeps,
its huge paw curled
upon a star-infested ear.

“How like humans,” he said drily. “The universe is vast, majestic, intricate, patterned with inexhaustible beauty, vivid with infinitely varied life—and there’s only one thing in it that really interests you. The same thing that makes you buy books, build families, create atomic theories (I imagine) or, once upon a time, write poetry. Sex.”

The whole universe is only the self with variations, one tune made bearable by variations. Sometimes there are discords, but they only make the subsequent harmony more perfect.

The universe was a language with a perfectly ambiguous grammar. Every physical event was an utterance that could be parsed in two entirely different ways, one causal and the other teleological.

The thing is, I mean, there’s times when you look at the universe and you think, “What about me?” and you can just hear the universe replying, “Well, what about you?”

Behold yon miserable creature. That Point is a Being like ourselves, but confined to the non-dimensional Gulf. He is himself his own World, his own Universe; of any other than himself he can form no conception; he knows not Length, nor Breadth, nor Height, for he has had no experience of them; he has no cognizance even of the number Two; nor has he a thought of Plurality; for he is himself his One and All, being really Nothing. Yet mark his perfect self-contentment, and hence learn this lesson, that to be self-contented is to be vile and ignorant, and that to aspire is better than to be blindly and impotently happy. Now listen." He ceased; and there arose from the little buzzing creature a tiny, low, monotonous, but distinct tinkling, as from one of your Spaceland phonographs, from which I caught these words, "Infinite beatitude of existence! It is; and there is none else beside It.