Were Pietro Mascagni and Ambroise Thomas both best known for their contrabution to theatre? 
Pietro Mascagni: Pietro Antonio Stefano Mascagni (] ; 7 December 1863 – 2 August 1945) was an Italian composer most noted for his operas. His 1890 masterpiece "Cavalleria Rusticana" caused one of the greatest sensations in opera history and single-handedly ushered in the "Verismo" movement in Italian dramatic music. Ambroise Thomas: Charles Louis Ambroise Thomas (5 August 1811 – 12 February 1896) was a French composer, best known for his operas "Mignon" (1866) and "Hamlet" (1868, after Shakespeare) and as Director of the Conservatoire de Paris from 1871 till his death.
yes