The Requiem was Mozart?s final composition. It was commissioned by the widow of the Countess von Walsegg who died in February 1791. After working on the Requiem through October and November however Mozart fell ill and died without completing it. Mozart's widow needing money asked Joseph Eybler to complete the work. Unfortunately he could not finish the work and it was handed over to Franz Xaver Sussmayr. However Sussmayr was a musician of limited capabilities and much of his contribution was in fact a copy of Eybler's work.