The first time I heard it, I didn't believe it. You never do, with moonlight. They didn't either, but then, they never tried to. It's not a sound, exactly. It's more of a sense. A combination of things that happen under that half-light.
Dew-jeweled grass whispering underfoot.
The velvet caress of lake and shore.
Fading leaves murmuring together as a soft breeze winds its way through tree limbs.
There's a gentle sighing, too. It's wonder, and light, and a sort of majesty, as the moon parts her veils of ink strewn with stars, and begins her journey across a silent world, illuminated by her lover as the world holds its sleep-heavy breath in admiration. For where the sun is a puppy's romp across a meadow, couples upon a pier, flowers turning their faces towards life, the moon is spiderwebs bedewed with frost, the flight of owl, an ocean's gentle acceptance of her gleam.
It's... ephemeral. Yet perhaps that's the reason why moonlight sounds as it does. I'd say it's breathtaking, but it's more than that. It's what encourages lungs to expand, hearts to pulse, minds to unpack their contents in search of... something which doesn't fade into inferiority with the comparison.
The second time I heard it, I was with them for a time. My girlfriend's glare as she went into the water alone. The snuffing of our barely-legal bonfire. Laughter-etched steps fading with the wind. The soft glow of plankton abruptly snuffed by surf's collision with sand. And the moon shrugging off twilit skies and rising to greet those who worshipped her cool fragility. It's luminescent elixir, that curious light.
The third time I stepped into that sea of incandescence, and swam through the sky, chasing constellations and weaving through her benevolent cloaks of onyx, teasing the mountains which reached for her and accompanying the birds who dared to scale the sky under her gaze.