I’m not exactly musically educated. I love to sing and I sing what’s put in front of me, but when the other members of my choir say “This is really interesting, for Mozart,” I simply have to believe them.
The song is No. 8 (from the Requiem) Domine Jesu, and it’s apparently the kind of stuff he was beginning to write when he died, making his death more tragic than it otherwise might have been. A bit like Heath Ledger, I guess, dying just as he was getting really interesting in his art.
The song is also beautiful. Amazing to sing. Here it is (like us, if we had a big hall, an orchestra and bad 80s hairdos):