The Allegro vivace Benedictus of a mass by this composer opens with a long keyboard solo. In the Pie Jesu of a mass by this composer, the basses start a fugue with the forte eighth notes “G, G, G,” dotted eighth “G” and sixteenth “F-sharp,” and quarter “F-sharp,” which repeat in the next movement. In 2019, Ulrich Leisinger published a complete reconstruction of a mass that this composer reused in his cantata Davide penitente. (15[1])The (*) Organ mass is one of three C major masses that this composer wrote within one year. In the first part of a mass by this composer, the basses sing “A, short A, F, high B-flat, (10[1])low C-sharp” to begin (10[1])a double fugue. (10[1])“Et incarnatus est” (10[1])is the last section that this composer wrote for his Great Mass in C minor. (10[2])In the 12/8 (“twelve-eight”) final section of a mass by this composer, all but the first (10[1])eight bars were written by Franz (10[1])Xavier Süssmayr. For 10 points, name this composer whose last of 18 masses was his unfinished Requiem. ■END■