“He was born in Schwanenstadt, Upper Austria, the son of a sacristan and teacher (who spelled the name Seissmayr, reflecting the Austrian pronunciation). His mother died when he was 6, and he left home at 13. He was a student and cantor in a Benedictine monastery (from 1779 to 1787) in Kremsmünster. When his voice changed, he became a member of the orchestra as a violinist.
The abbey performed operas and Singspiele, so he had the opportunity to study the operas of Christoph Willibald Gluck and Antonio Salieri. He composed a number of stage works and a good deal of church music for the abbey.
He became (after 1787) a student of Salieri in Vienna. In 1791 he assisted Wolfgang Amadeus Mozart as a copyist with La clemenza di Tito and Die Zauberflöte and is presumed to have written the secco recitatives in the first. Their relationship was close and playful, to judge by surviving letters to Constanze, whom Süssmayr accompanied to Baden.
For many years he was also thought to have been a student of Mozart, but there is reason to think that the notion of such a relationship was concocted by Mozart’s wife Constanze in order to legitimize his completion of Mozart’s Requiem. During Mozart’s last days, it is possible that they discussed his Requiem, and Süssmayr took on the task of completing the piece upon his death and did so, turning it over to Constanze within 100 days of Mozart’s death. Süssmayr’s version of the score is still the most often played, although several alternative versions have been written.”
[from Wikipedia]

Yeah, what’s up with this whole Sussmayr thing? According to Harnoncourt in no circumstances could he complete Mozart’s work. (Who did it then?) As far as I am concerned there are more “Mozart Requiems” and the one under the name of Sussmayr has its own life and has been proven to engage musicians and audiences despite its flaws. This is the version I have played many times as a young clarinet player (Oh, those cold churches in Hungary around Christmas time!) and this is the version we performed yesterday with the Huntsville Symphony in front of a full house at the Von Braun Center. The concert started with Mozart’s Masonic Funeral Music (another gorgeous piece using Basset horns) and we performed Haydn Symphony #93 before intermission. Our trumpet and horn players –as adventurous as they are– decided to use natural horns for the entire show. It sounded great and added an extra layer of artistry to the show.
Fun fact: I am traveling to Hungary today where I am doing a new music show next week. One of the pieces is going to be “Into The Little Hill”, a mesmerizing chamber opera by British composer George Benjamin. Guess what, he uses not one but two Basset horns (and Contrabass Clarinet among other “unusual” instruments) just like Mozart in his Masonic Funeral Music and Requiem. I love the sound of the Basset horns!