In one of the final scenes of the film Amadeus, Mozart on his deathbed dictates to his rival Salierei the music of a Requiem Mass, commissioned a few weeks earlier by a mysterious, masked stranger. But is this what really happened? What is the true story of the Requiem by Mozart? Following traces of what we can consider an intriguing historical mystery, we will be able to answer some of these questions by analyzing the structure of the work and the characteristics of the structure of Mozart’s choral composition.