Complex sentence: Palestrina is an opera (called by him a "Musikalische Legende") by the German composer Hans Pfitzner, first performed at the Prinzregententheater, Munich on 12 June, 1917.
Split into simpler sentences: Palestrina is an opera (called by him a "Musikalische Legende") by the German composer Hans Pfitzner. It first performed at the Prinzregententheater, Munich on 12 June, 1917.