Mozart’s Requiem is completed anew

Michael Ostrzyga at rehearsal with the Harvard Summer Chorus.Jim Davis/Globe Staff

When you listen to Mozart’s celebrated Requiem, you’re not just hearing music by Mozart. The composer died at the early age of 35, leaving the piece unfinished, and the story of the Requiem and the circumstances surrounding it has been told and re-told, exaggerated and exploited. (Forget what you saw in “Amadeus.”)

From the day of Mozart’s death to the present, the incomplete work has continually fascinated listeners and scholars, and the Harvard Summer Chorus’s program this year makes a new take on the Requiem its cornerstone. German composer and conductor Michael Ostrzyga will conduct the world premiere of his completion on Friday at Harvard Yard’s outdoor Tercentenary Theatre and Sunday in a Monadnock Music concert at the Peterborough Town House in Peterborough, N.H. Joining the chorus will be the Boston Modern Orchestra Project.

Ostrzyga, who is music director at the University of Cologne in Germany, has conducted the Requiem several times. “For me, always, the genius of Mozart is that he was so secure what to write in every aspect of his piece. It was in his head and he just had to write it down,” he said in an interview in Cambridge.

But in this case, Mozart didn’t get to “write it down.” The composer died suddenly, with the “Introitus” and “Kyrie” movements complete and the “Sequentia” and “Offertorium” movements in detailed sketches. The most frequently performed version of the Requiem was finished by Mozart’s copyist, Franz Xaver Sussmayr, months after the composer’s death.

Myriad questions surround the music. In an 1800 letter, Sussmayr claimed that he had completed the “Lacrymosa,” Mozart’s sketch of which cuts off after eight bars, and that the final movements were “composed afresh” by Sussmayr. It may never be known what other sketches and scraps may have been lost, or what verbal instructions Sussmayr may have received from Mozart regarding the unfinished movements. However, it is commonly agreed that Sussmayr’s contributions incorporate some very un-Mozartean writing.

“Sussmayr didn’t try to write it in Mozart’s style. He just finished it,” clarified Harvard University director of choral activities Andrew Clark, who became friends with Ostrzyga when the Harvard Collegium Musicum toured Germany and Austria in 2011. Sussmayr had been working on a tight deadline after the composer’s death, because if the composition was not delivered to its commissioner, Mozart’s widow and young children would have been in dire financial straits. That completion of the Requiem has been criticized as amateurish for centuries. Musicologist Richard Maunder’s book on his own completion of the Requiem spares no invective, calling Sussmayr’s writing “clumsy and unimaginative” and an “extraordinary muddle.”

Ostrzyga takes a more affirmative stance on Sussmayr, saying his work deserves to be appreciated, while acknowledging a discernible “breach” in the music between Mozart’s material and Sussmayr’s. In his completion, Ostrzyga tries to emulate Mozart’s conventions as much as possible. “I couldn’t be Mozart, so I tried to be the one who got the instructions by Mozart, and the one who has access to everything Mozart wrote,” he said.

Clark described Ostrzyga’s approach as similar to that taken by Harvard professor emeritus Robert Levin, whose completion of the Requiem has been performed several times at Harvard and recorded by Boston Baroque. To complete the piece, Ostrzyga researched the path of the Requiem through different composers who attempted to complete it before the task fell to Sussmayr, and he analyzed Mozart’s other music, sacred and secular, in search of a roadmap to what may have emerged had he lived.

This sometimes involved setting aside his own instincts or desires, as in the “Domine Jesu” section of the “Offertorium” movement. “In the sketch, there’s just this . . . ” he said, and sang the simple figure for the low instruments. “Freystätdtler [a composer who worked on the Requiem before Sussmayr] wrote in there these complicated violin figures in canon. . . . As a teenager, that was one of my favorite string writings there in the Mozart requiem, so I wanted to keep it, and I had to decide, is this truer to what Mozart would have done?” He considered a completed earlier piece with similar choral writing and decided Mozart would have taken a more straightforward approach.

“There really is no other work in the canon that lends itself to this kind of hypothesis, conjecture, and forensics,” said Clark.

The Harvard Summer Chorus is a community ensemble, with everyone from high schoolers to senior citizens, and for some, this fresh take is their first encounter with the Requiem. But those who have sung the piece before are noticing the differences. “I think part of the appeal of singing this summer was to explore a new completion,” Clark said. “There’s one member of the chorus who has performed Sussmayr, Robert Levin, Duncan Druce . . . he’s a collector of Mozart completions.”

HARVARD SUMMER CHORUS

At Tercentenary Theatre, Harvard University, Cambridge, on Friday, 8 p.m., free; and presented by Monadnock Music at Peterborough Town House, Peterborough, N.H., Sunday, 3 p.m. $30. summer.harvardchoruses.fas.harvard.edu, www.monadnockmusic.org