Orlando di Lasso, also known as Roland de Lassus lived from about 1532-1594. He was one of a few great Belgian composers. He composed mainly sacred music and was another composer similar to Giovanni Pierluigi da Palestrina. Lasso's forte was the motet, not the mass though. He composed over 2000 pieces, rivaling Bach in volume. Also, Lasso composed in ALL of the prevelent styles of the day. He composed Italian madrigals, french chansons, and motets, particularly motets. Amazingly, he also spoke and composed in his native Italian, French, German, and Latin. His main treatise on motets was the "Magnum Opus Musicum" (The Great Work of Music). It was published after his death, by his sons in 1605.
Lasso used few new and different musical styles, but took 16th century sacred music to its' pinnacle. He, like other composers, used suspensions and deceptive cadences to build tension. His sacred music was influenced largely by the Counter-Reformation. His main achevement wasn't in trying new things, but mastering all of the current compositional techniques and styles. His was influenced by French, German, Italian, and Franco Flemish composers like Adrian Willaert.
This information was found in my IB music class notes and in chapter 8 of the "History of Western Music", 6th ed.