Robert Levin is one of several recent composers to create a version of this work, in which a bass soloist duets with a trombone at the start of "Tuba 
Robert Levin is one of several recent composers to create a version of this work, in which a bass soloist duets with a trombone at the start of "Tuba Mirum," while the four vocal soloists sing in counterpoint near the end of "Domine Jesu Christe." Franz Sussmayer was one of the most notable people to try completing this work, which has a double fugue at the end of the "Kyrie." It also includes the bleak "Dies Irae" and "Lacrymosa." For 10 points, name this final entry in the Kochel catalogue, an unfinished funeral mass by the composer of Don Giovanni.
Robert Levin is one of several recent composers to create a version of this work, in which a bass soloist duets with a trombone at the start of "Tuba Mirum," while the four vocal soloists sing in counterpoint near the end of "Domine Jesu Christe."
Johann Christoph Wolfgang Amadeus {Mozart's Requiem Mass in D Minor} [prompt on Requiem or similar answers that do not specify Mozart]