At age three, Agostini moved with his family to Montreal, Quebec, Canada. His father, Giuseppe Agostini, was a composer and conductor and it is from him that he had his initial musical training beginning at age five. He later pursued further studies in harmony and composition with Louis Michiels and Henri Miro and in cello with Peter Van der Meerschen.
At 16, Agostini was playing with the Montreal Philharmonic Orchestra as a cellist and was a part-time band player in a nightclub band playing saxophone and clarinet. From 1932 to 1943, he composed film music for the Associated Screen News of Canada newsreels, and in 1934 he began working as a conductor for the Canadian Radio Broadcasting Commission (the forerunner to the Canadian Broadcasting Corporation). In Toronto, where he moved in 1943, he composed and conducted the incidental music for drama series and variety programs on the CBC radio and television, and for over 20 years he held the position as conductor and arranger on the popular weekly series Front Page Challenge. As a composer, he wrote for The Tommy Ambrose Show and The World of Music, musicals, scores for movies (including a brief stint in Hollywood from 1955–56), shorts (many for the National Film Board of Canada’s Canada Carries On and The World in Action series), concertos and an opera.
- Conductor led first CBC program at 18, The Globe and Mail, The Arts, Saturday, 17 February 1996. C2. accessed on 18 October 2006.