The Sicilian-born Mannino studied piano and composition at the Rome Conservatory, and came to Ottawa in 1982. In 1986 he was appointed principal guest conductor, a position he held until 1989.

Of working with Mannino, known for his enthusiasm and rigorous rehearsals, Ian Bernard, the orchestra's principal timpanist, said, "It was sheer emotion and a sort of tension in the rehearsal, just unbelievable. You would finish a rehearsal and you felt sort of like you had just made love. You were emotionally drained, a feeling I never had with many other conductors."

Mannino was also a composer, writing music for more than 100 films, including films by his brother in law, director Luchino Visconti. Mannino won a David di Donatello award for the score for Visconti's L'innocente.