The first part of this introduction deals extensively with the history and reception of the Requiem. This is followed by an in-depth documentation of Ostrzyga's Requiem Edition. In addition, this introduction represents the first comprehensive analytical study of the Requiem based on historically informed music theory and artistic practice (especially in composition, instrumentation, and arrangement). It clears up numerous prejudices against Süßmayr's work, which are also widespread in the scholarship literature, and also discusses problems of previous attempts at finishing or arranging the Requiem.