Even after his retirement from opera, he continued singing in benefits and concerts, the very last of which was in 1904, when Cotogni was 73. Cotogni's repertoire comprised between 150 and 160 roles. His operatic triumphs were not confined to Verdi's compositions. He was also an exponent of the elegant but technically demanding "bel canto" music of Gioachino Rossini, Gaetano Donizetti, Vincenzo Bellini, and Saverio Mercadante. He sang roles from the new Italian verismo literature, the French grand opera tradition, and some Wagner. He was considered a Mozart specialist and keeper of some traditions of his works, even at a time when Mozart's works were not popular. He was particularly proud of his "Don Giovanni", a role that he learned from his predecessor, the Italian baritone Antonio Tamburini, and which Cotogni then passed on to the inheritor of his traditions, Mattia Battistini. Cotogni sang in the company of many of the most famous opera singers of his time—sopranos Adelina Patti, Teresa Stolz, Thérèse Tietjens, Marcella Sembrich, Christina Nilsson, Emma Albani, and Gemma Bellincioni; castrato Alessandro Moreschi; the Marchisio sisters; contralto Sofia Scalchi; tenors Mario, Francesco Marconi, Julián Gayarre, Angelo Masini, Pietro Mongini, Lodovico Graziani, Enrico Tamberlick, and Francesco Tamagno; baritones Charles Santley, Jean-Baptiste Faure, Francesco Graziani, Leone Giraldoni, and Mattia Battistini; and basses Foli, Eraclito Bagagiolo, and Édouard de Reszke.