 De Masi became interested in film music when Longo was asked to compose a soundtrack for a film, and he asked De Masi to be his assistant.De Masi's filmography includes scores for over 200 films and TV series, ranging from spaghetti westerns and sword and sandal epics to gialli and horror films, such as Lucio Fulci's "Lo squartatore di New York" ("The New York Ripper").De Masi also scored several action films, such as Enzo G. Castellari's "Quel maledetto treno blindato" ("The Inglorious Bastards"), but he is best remembered for his work on spaghetti westerns.