"...like a rusty squeezebox..."

This is Wolfgang Amadeus Mozart's "Serenade Nº 10 for winds in B flat major, "Gran Partita," its third movement, "Adagio."
Performed by the Orchestre des Champs-Élysées, conducted by Philippe Herreweghe.

In Miloš Forman's superb movie "Amadeus," here's how Antonio Salieri describes this music:
"On the page, it looked... nothing!
The beginning simple, almost comic.
Just a pulse: bassoons, basset horns, like a rusty squeezebox!
And then, suddenly, high above it, an oboe!
A single note, hanging there, unwavering, until a clarinet took it over, sweetened it into a phrase of such delight!
This was no composition by a performing monkey!
Yes, it was music I had never heard.
Filled with such longing, such unfulfilled belonging!
It seemed to me I was hearing the voice of God!"

What more could one say?