The Amen fugue – orientation to Johann Sebastian Bach
For his newly executed Amen fugue at the end of the Lacrimosa, which is based on a sketch by Mozart, Ostrzyga orientated himself to Bach. For example, Bach’s D minor fugue (BWV 851) from The Well-Tempered Clavier I closes with the opening of the theme presented in this multiple combination of the original and its inverted form:
The hexachord theme, which Mozart left behind in his Amen sketch as the main part, practically corresponds with the theme of Bach’s keyboard fugue. There, only the very first note is “missing”.
Inspired by Bach’s concept for the end of the keyboard fugue, Ostrzyga designed a comparable construction for the end of the Amen fugue taking into consideration the other starting position of Mozart’s sketch and transferring its material with smaller note values to the violins; in principle this approach is modelled on the ending of the Cum sancto spiritu fugue from Mozart’s Great Mass in C Minor K. 427.
This example shows how Ostrzyga incorporated Bach’s, but also Mozart’s techniques in the missing parts of the Requiem.
However, Mozart’s Amen sketch – in contrast to the fragment score of the Requiem – has to be viewed as being of a preliminary nature. It is conceivable that, while writing out the fair copy of the score, he would have dismissed the Amen fugue. Therefore, Ostrzyga leaves it up to the performers whether or not they wish to conclude the Lacrimosa with the Amen fugue.