rationalskepticism.org

Most of Mozart's Requiem was composed by Süssmayr. 'Stansi was OK with the subterfuge regarding its authorship, for the piece was commissioned by Count Franz von Walsegg, and she needed the money. The count might have been somewhat reluctant to pay for it had she let up that her husband had died before he got beyond completing the first movement, sketching out the second, and possibly - just possibly - a couple more.

Still, a great work. Süssmayr seems to have been truly inspired by what Wolfie had left behind.

There must be hundreds of recordings of that piece. Here is one of them.

https://www.youtube.com/watch?v=-1DsJ5YQr5s