Johann Heinrich Köselitz (10 January 1854 – 15 August 1918) was a German author and composer. He is known for his longtime friendship with Friedrich Nietzsche, who gave him the pseudonym Peter Gast. Life. Köselitz was born in Annaberg, Saxony to Gustav Hermann Köselitz (1822–1910), the vice mayor (Vizebürgermeister), and his wife Caroline (1819–1900), a native of Vienna. His younger brother was the painter Rudolf Köselitz. From 1872, Köselitz studied music with Ernst Friedrich Richter at the University of Leipzig.
https://en.wikipedia.org/wiki/Heinrich_K%C3%B6selitz