Complex sentence: Mario bade farewell to the stage at Covent Garden in 1871, but his last performances were concerts in a U.S.A. tournée with Carlotta Patti in 1872-73.
Split into simpler sentences: Mario bade farewell to the stage at Covent Garden in 1871. But Mario's last performances were concerts in a U.S.A. tournée with Carlotta Patti in 1872-73.