Settings also exist by Mozart , Byrd , Elgar , Verdi , Saint-Saens , Rossini , Brahms and Perosi as well as numerous versions by less well-known composers , such as J.B. Tresch . Settings also exist by Mozart , Byrd , Elgar , Saint-Sa Ã `` ns , Rossini , Brahms , Stravinsky , Lauridsen , and Perosi as well as numerous versions by less well-known composers , such as J.B. Tresch .