So I have to come up with the whole thing right now, with no prep, and it can't be something I've thought of before?
Ok, this is what you get;
THE MUSIC OF MUTE
A world where time and moment are defined by song. Where light and space are like music and music is audible physics. The sun rises to a single note. The stars are distant cold harmony. The song of evening pales the world.
Reality can shift like music, but it cannot be discordant to itself. (Except Monsters, they are discordant, they are bad notes.)
The note of the sun allows the existence of the beats and rhythms of the material world.
Nothing on Mute can make a sound, it would interrupt the Music. As if living things could re-program the cosmos at a basic level. Maybe Wizards sing, or speak.
Material things fade in as the note of dawn grows louder. Not every material thing is described by its own motif, or even note, but the substance of things must be in harmony with the everpresent song. If the music is low, soft and sad, that might be fog, a still sea, a drooping forest, but it couldn't be a raging fire, supergothic mountains or a crashing waterfall.
The music is never in counterpoint to the world - it is Reality.
Perceived realities must cohere. Sophonts leave snail-trails of perceived reality behind them.
So as a whole its more like a 'real world' than you would suppose. Mutual interacting triangulations of sense produce a reasonably solid consensus wherever sophonts gather. When they are off on their own, and they meet each other, realities merge.
Listening well is a meaningful skill. Those who can perceive and predict the deep structures of the music of Mute have a kind of reality meta-sense. They can make very very strong and very accurate guesses about when and how they qualities of the world can change
Sense a rising theme
"To know the song, the ears and the earth, this is wisdom" - philosophers might sign to each other.
Meaning you have to understand the music, understand how others (and yourself) will perceive the music, and understand the realities as they exist.
Differing kinds of expertise in listening depend on the time signature of familiarity. Someone good at note-to-note tonality might be a great duellist, fighter, gambler or dancer. Someone good at the medium range might be a great explorer, sailor, trader, climber or worker in a complex environment. Someone good at very deep and very long structural changes might be a great general, philosopher, engineer of megastructures, prophet or cultural guide.
Movement is music and language on Mute. Writing is frozen movement. Musical script is silence and magic. The construction of instruments is high science - like Hadron Collider scale stuff and they can only make maybe one note with great difficulty.
Underground is like a static hiss but touching or feeling things reveals music hidden in the static. So does digging your hand into fresh soil.
Concentrating on something others can't sense is like hearing one conversation in a crowd, or one theme hidden in deep music - it was always there but you couldn't 'hear' it until now.
Is there divergent evolution on Mute?
I would have to say no as the revisions would push the world out of anything easily conceived of. So this is more a fairytale world with different rules but mysteriously similar forms and structures.
But it would be fun to do the full Arnold K version with alternative evolution and entirely different forms - super-display creatures, semaphore giraffe’s and hundred-handed men.