It was written (though not completed) in the Classical Era, and in the very last days of Mozart's life.
Latin
It's the Lacrimosa section from Mozart's Requiem Mass.
Wolfgang Amadeus Mozart
The average BPM of the Lacrimosa movement in Mozart's Requiem is around 80 beats per minute.
Requiem
Mozart's Mass Requiem.
Requiem Mass
The time signature of the lacrimosa movement in Mozart's Requiem is 4/4, which means there are four beats in each measure.
In order to celebrate his life, she wrote a requiem.
Ignaz Franz Mosel has written: 'Ueber die original-partitur des Requiem von W.A. Mozart'
Try Mozart's Requiem
Almost every composer of renown has one. Mozart and Leonard Bernstein each have famous ones.