Heinrich Köselitz

In 1877, Köselitz sharply criticized the Basel music instructor Selmar Bagge in a newspaper article[clarification needed], which led to a minor scandal.

Köselitz was instrumental in the preparation of all of Nietzsche's works after 1876, reviewing the printer's manuscript and sometimes intervening to finalize the text formatting.

Peter Gast's most ambitious musical work is the comic opera in three acts The Lion of Venice (Der Löwe von Venedig).

It premiered in February 1891 in Danzig under the direction of Carl Fuchs, who exchanged letters with Nietzsche, but under its original title The Secret Wedding (Die heimliche Ehe or Il matrimonio segreto).

In addition to being a musician and the editor of Nietzsche's writings and letters, he worked as a writer under various pseudonyms, including: Ludwig Mürner, Peter Schlemihl, Petrus Eremitus.

Köselitz would "correct" Nietzsche ’s writings even after the philosopher's breakdown and did so without his approval - something heavily criticized by today's Nietzsche scholarship.