This document lists important operas composed between 1874-1905 by several famous composers including Humperdinck, Leoncavallo, Mascagni, Mussorgsky, Puccini, Strauss, Tchaikovsky, Verdi, and Wagner. Some of the operas listed include Hänsel und Gretel, Pagliacci, Cavalleria rusticana, Boris Godunov, La bohème, Salome, Eugene Onegin, and Siegfried. The document provides a list of influential operas from the late 19th and early 20th centuries.