He had an unparalleled reputation as a coach of young opera singers and famously harnessed and developed both Renata Tebaldi's and Maria Callas's considerable talents.
He took over as Music Director at La Scala when Toscanini left to go to New York, and served 1909–1914, 1917–1918, and returned briefly after the Second World War, 1946–1947.
This included many operas that are seldom performed, by composers such as Alfano, Catalani, Giordano, Massenet, Montemezzi, Monteverdi, Pizzetti, Respighi, Rimsky Korsakov, and Zandonai.
[3] Serafin was instrumental in expanding the repertory, conducting the Italian premieres of works by Alban Berg, Paul Dukas, and Benjamin Britten.
He also conducted important world premieres by both Italian and American composers, such as Franco Alfano, Italo Montemezzi, Deems Taylor, and Howard Hanson.