Guerrini worked as both a professional violinist and violist in orchestras in Bologna in the 1910s. He also periodically worked as a guest conductor at theaters in Bologna, including conducting operas at the
Teatro Comunale di Bologna when a substitute conductor was needed. During
World War I he served in the
Italian Army. In 1922 he married Emilia Putti, and in 1923 their daughter Vittoria was born. From 1920 through 1924 Guerrini taught on the faculty of the
Bologna Conservatory as a professor of
harmony. He then joined the staff of
Parma Conservatory where he taught from 1925 to 1928; holding the post of chair of music composition. He was appointed director of the
Florence Conservatory in 1928; a post he held until 1947. He subsequently served as director of the
Bologna Conservatory from 1947 through 1949, and as director of the
Conservatorio Santa Cecilia from 1950 until his retirement in 1960. He was later name president of the
Accademia Nazionale di Santa Cecilia in 1964; a position he held until his death the following year. Guerrini was also part of an executive committee over the
Maggio Musicale Fiorentino from 1931 to 1933. That opera festival presented the premiere of an opera he co-wrote with A. Testoni,
La vigna, in 1935. During
World War II, he was imprisoned in an
Italian Fascist concentration camp in
Collescipoli,
Terni from December 1944 through August 1945. He wrote his opera
Enea while in this camp. The work was staged at the
Teatro dell'Opera di Roma in 1953. He also wrote a choral piece,
Missa quarta, which was first sung in the camp on Christmas Day 1945. From 1952 to 1957, he was director of the Rome Chamber Orchestra (Italian: Orchestra da camera di Roma). During his career he also wrote music criticism for a variety of Italian publications. Guerrini died in
Rome on June 14, 1965, at the age of 74. ==Composer==