Remarks:
This came out in 1792, a year after his death. It did not chart, but it is easily my favourite piece of his music. It is sung in Latin because back then the Cathollic Mass was sung in Latin. It still is in some places, a practice that Pope Francis is trying to make even rarer than it already is.
See also:
Lyrics: the video has both the Latin lyrics and an English translation.
Abagond 
One of my favorite pieces of music ever. The first time I heard it was a few weeks into Latin 1. My professor played snippets of each movement and then translated some of the lyrics. Directly after class, I went to the audio center at the library and listened to the whole Requiem on LP, absolutely transfixed.
It actually was unfinished at the time of Mozart’s death. Süssmayr wrote the bulk of the remainder, working from Mozart’s notes and some educated guesswork.
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