This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Mozart composed across nearly every genre of his time: symphonies, concertos, chamber music, and operas including The Marriage of Figaro, Don Giovanni and The Magic Flute, a range few composers of any era have matched across so many different musical forms simultaneously rather than specializing in one or two. His final work, a Requiem Mass commissioned anonymously in 1791, was left unfinished at his death and completed by his student Franz Xaver Sussmayr, so the Requiem that has been performed and recorded ever since is, in its final movements, partly the work of a student finishing his teacher's own unfinished score.
He completed more than 800 catalogued works in a career of barely three decades and died at thirty five, a rate of output that has made the sheer size of his catalogue, set against the shortness of the life that produced it, one of the most frequently cited facts about him in every account of his career since. The Requiem's own unfinished state at his death is itself a detail that has attracted more attention than almost any other single fact about his final months, precisely because it leaves a documented, specific gap between what Mozart himself wrote and what audiences have heard credited to his name ever since.