Trained originally as a violinist, Frosali established as a violinmaker in Florence in 1932 having studied with Giuseppe Scarampella. Emigrating to America, he worked first in New York where he worked for Emil Herrmann. While there he worked alongside Simone Sacconi. He moved to Los Angeles in 1939 working at Wurlitzer in their violin department, establishing his own shop in 1954. In 1949 he was the only American maker to win an award at a major competition in the Hague.  He was enormously successful and his instruments were (and still are) in great demand both in the Los Angeles area as well as here in the Bay Area.