I also have a feeling that Schutz did not quite get his facts straight, particularly with regard to Mozart's attitude towards the texts he set. Schutz gave the impression that Mozart did not pay very much attention to the words, even in his operas, figuring that it did not matter very much what those words were as long as they advanced the plot in the proper direction. Schutz then added the following:
Moreover, Mozart did not hesitate to change the dramatic structure of his operas, here inserting an aria for a favorite singer, there leaving out one not suitable for the performer, and even dropping for the Viennese production the last scene of Don Giovanni, where the survivors rush in after the hero's disappearance, merely because the opera would have been too long by reason of the numbers added for that performance.Other sources tell a different story about the conclusion of Don Giovanni. The story is that Mozart wanted to end the opera with the Don being dragged down to Hell. Unfortunately, this did not go down well with the moralists. It was not enough that vice be punished; virtue must also be rewarded. Thus, Lorenzo Da Ponte came up with a text in which all the other (living) characters talk about going on to live a better life (which, in Donna Anna case, means not rushing to the marital bed with Don Ottavio). Mozart's setting is a perfectly ravishing sextet, yet another shining example of how he could work with so many different voices without compromising the individuality of any of them. However, the signs seem to be that his heart was not in this one, since, for him at least, it was an anticlimax to the way in which he thought the Don's story ought to be told.