It is the composer 's only completed opera and is considered an important work of the second half of the 20th century .
Zimmermann himself faithfully adapted the play into the libretto , the only changes to the text being repeats and small cuts .
Zimmermann is the composer 's only completed opera and is considered an important work of the second half of the 20th century .
Zimmermann himself faithfully adapted the play into the libretto , the only changes to the text being repeats and small cuts .