When Johannes Brahms stumbled upon Bach’s “Chaconne” in 1877, he simply couldn’t believe his eyes. “On one stave, for a small instrument, the man [Bach] writes a whole world of the deepest thoughts and most powerful feelings. If I imagined that I could have created, even conceived the piece, I am quite certain that the excess of excitement and earth-shattering experience would have driven me out of my mind.”
To answer the original question
Mozart PC No.23
Right, that's that question decided now what's next
Great topic. And I enjoyed listening to some of the suggestions for the first time,
The serious replies to this question refer to works that were written a century or more ago. Pehaps a naive question and perhaps it has been discussed elsewhere, but is there any possibility that another work of the same level of craftsmanship, depth and beauty will be written in the near future? Why not?
The Grosse Fugue without any doubt. We are a poorer species if indeed Beethoven did not have children.
I love Muzio Clementi's music.
I don't go for "greatest", but my one of my favourite pieces at the moment is Beethoven's deservedly famous String Quartet No. 14. Hard to pick a favourite movement, but how about the fourth (the theme & variations)?